oiiotool: attribute actions get subimage controls (#3384)

I realized that --attrib (and several related actions) only set the
attribute as directed for the first subimage if it's a multi-image
file (such as a multi-part exr), or all of them if the -a flag is
used.  But there was no ability to set it for a particular (non-first)
subimage, like many other oiiotool actions have the ability to do.

So in this patch, I refactor the following commands to use the
OiiotoolOp and related macros, which automatically make it responsive
to the `:subimages=` optional modifiers:

    --attrib
    --sattrib
    --eraseattrib
    --caption
    --orientation
    --clear-keywords
    --iscolorspace

As a bonus aside, one thing this lets you do is set a different
compression method per-subimage using, e.g.,
`--attrib compression:subimages=3 dwaa:100`.
But if you set compression with `--attrib compression`, do not also
use `--compression`, which will override it and also apply to all
subimages.

src/doc/oiiotool.rst

@@ -1767,8 +1767,14 @@ current top image.
 
     Optional appended modifiers include:
 
-    - `type=` *typename* : Specify the metadata type.
-
+      `:subimages=` *indices-or-names*
+        Include/exclude subimages (see :ref:`sec-oiiotool-subimage-modifier`).
+        Only included subimages will have the attribute changed. If subimages
+        are not set, only the first subimage will be changed, or all subimages
+        if the `-a` command line flag was used.
+
+      `:type=` *typename* : Specify the metadata type.
+
     If the optional `type=` specifier is used, that provides an explicit
     type for the metadata. If not provided, it will try to infer the type of
     the metadata from the value: if the value contains only numerals (with
@@ -1780,24 +1786,43 @@ current top image.
 
     Examples::
 
+        # Set the IPTC:City attribute to "Berkeley"
         oiiotool in.jpg --attrib "IPTC:City" "Berkeley" -o out.jpg
     
+        # Set a name attribute to "0", but force it to be a string
         oiiotool in.jpg --attrib:type=string "Name" "0" -o out.jpg
     
+        # Another way to force a string attribute using --sattrib:
+        oiiotool in.jpg --sattrib "Name" "0" -o out.jpg
+    
+        # Set the worldcam attribute to be a matrix
         oiiotool in.exr --attrib:type=matrix worldtocam \
                 "1,0,0,0,0,1,0,0,0,0,1,0,2.3,2.1,0,1" -o out.exr
-    
-        oiiotool in.exr --attrib:type=timecode smpte:TimeCode "11:34:04:00" \
-                -o out.exr
 
+        # Set an attribute to be a timecode    
+        oiiotool in.exr --attrib:type=timecode smpte:TimeCode "11:34:04:00" -o out.exr
+
+        # Set an attribute in all subimages
+        oiiotool multipart.exr --attrib:subimages=all "Foo" "bar" -o out.exr
+
+        # Set an attribute just in subimages 0 and 3
+        oiiotool multipart.exr --attrib:subimages=0,3 "Foo" "bar" -o out.exr
 
 .. option:: --caption <text>
 
     Sets the image metadata `"ImageDescription"`. This has no effect if the
     output image format does not support some kind of title, caption, or
-    description metadata field. Be careful to enclose *text in quotes if you
+    description metadata field. Be careful to enclose *text* in quotes if you
     want your caption to include spaces or certain punctuation!
 
+    Optional appended modifiers include:
+
+      `:subimages=` *indices-or-names*
+        Include/exclude subimages (see :ref:`sec-oiiotool-subimage-modifier`).
+        Only included subimages will have the attribute changed. If subimages
+        are not set, only the first subimage will be changed, or all subimages
+        if the `-a` command line flag was used.
+
 .. option:: --keyword <text>
 
     Adds a keyword to the image metadata `"Keywords"`.  Any existing
@@ -1806,7 +1831,7 @@ current top image.
     effect if the output image format does not support some kind of keyword
     field.
 
-    Be careful to enclose *text in quotes if you want your keyword to
+    Be careful to enclose *text* in quotes if you want your keyword to
     include spaces or certain punctuation.  For image formats that have only
     a single field for keywords, OpenImageIO will concatenate the keywords,
     separated by semicolon (`;`), so don't use semicolons within your
@@ -1816,6 +1841,14 @@ current top image.
 
     Clears all existing keywords in the current image.
 
+    Optional appended modifiers include:
+
+      `:subimages=` *indices-or-names*
+        Include/exclude subimages (see :ref:`sec-oiiotool-subimage-modifier`).
+        Only included subimages will have the attribute changed. If subimages
+        are not set, only the first subimage will be changed, or all subimages
+        if the `-a` command line flag was used.
+
 .. option:: --nosoftwareattrib
 
     When set, this prevents the normal adjustment of "Software" and
@@ -1832,6 +1865,14 @@ current top image.
     Removes any metadata whose name matches the regular expression *pattern*.
     The pattern will be case insensitive.
 
+    Optional appended modifiers include:
+
+      `:subimages=` *indices-or-names*
+        Include/exclude subimages (see :ref:`sec-oiiotool-subimage-modifier`).
+        Only included subimages will have the attribute changed. If subimages
+        are not set, only the first subimage will be changed, or all subimages
+        if the `-a` command line flag was used.
+
     Examples::
 
         # Remove one item only
@@ -1841,7 +1882,7 @@ current top image.
         oiiotool in.jpg --eraseattrib "GPS:.*" -o no_gps_metadata.jpg
     
         # Remove all metadata
-        oiiotool in.exr --eraseattrib ".*" -o no_metadata.exr
+        oiiotool in.exr --eraseattrib:subimages=all ".*" -o no_metadata.exr
 
 
 .. option:: --orientation <orient>
@@ -1852,6 +1893,14 @@ current top image.
     displayed, it does NOT alter the pixels themselves, and so has no effect
     for image formats that don't support some kind of orientation metadata.
 
+    Optional appended modifiers include:
+
+      `:subimages=` *indices-or-names*
+        Include/exclude subimages (see :ref:`sec-oiiotool-subimage-modifier`).
+        Only included subimages will have the attribute changed. If subimages
+        are not set, only the first subimage will be changed, or all subimages
+        if the `-a` command line flag was used.
+
 .. option:: --orientcw
             --orientccw
             --orient180