Image sequence import: .tif support

[mlavik1]

Thanks to #29 we now have image sequence import!
However, unity does not support TIF textures.
We can solve this easily by using FreeImage.
I made an async texture importer for unity that suports TIF a while ago: https://codeberg.org/matiaslavik/unity-async-textureimport/
We could use that, but it's probably better to just take the FreeImage bindings from that project.
Note: That project only works in Windows and Linux.

[mlavik1]

Supported through SimpleITK.