[Java] Refactor javadoc

[lastsecondsave]

Javadoc's syntax hasn't been changed since tmLanguage era and there are so many things wrong with it so I just redid it from the scratch.

'Strategic' changes:

1. Syntax is now hidden. It is part of Java, by itself it's pointless.
2. It is not included anymore, it now relies on new embed/escape functionality. This fixes issue [Java] Javadoc can 'escape' its bounds #1216.
3. URL's highlighting was removed. It isn't part of the javadoc, links are defined with html's <a> tag (which is already highlighted).

Fixes/improvements:

1. One-line javadocs now work.
2. Leading html tag doesn't turn off the highlighting.
3. Lines without leading asterisk are not treated as invalid anymore. The asterisk is optional since 2002.
4. All inline tags can now be multiline. They do not re-highlight the leading asterisk.
5. 'code' tag now supports brackets' balancing.
6. 'link' tag has reference and label scoped properly. Label can now contain html tags.
7. 'param' tag has its parameters highlighted. Type parameter is not recognized as html tag anymore.
8. 'see', 'throws' and other tags with reference now have this reference recognized.
9. Added new tags from Java 8 and 9.

Before:

After:

[lastsecondsave]

BTW this also fixes issue #966

[FichteFoll]

Always love seeing screenshot comparisons of PR changes.

Python needs this too. Primarily for the sphinx style, which is the easiest to recognize correctly, but there are other docstring styles that I haven't studied yet wrt their distinguishability.

[wbond]

Awesome, thanks for this!

[rwols]

Perhaps we can use this in C/C++/ObjC/ObjC++ too?

[wbond]

@rwols Do people use Javadoc in C languages?

[rwols]

No, but it's so similar to Doxygen, I wonder if it'll "just work".