Fix parameter type in get_info()
Implement some properties in our Uploader subclass that can be queried on upload failure
Display some more useful error messages when the upload failed on what seems to be an unsupported file
Make error message strings translatable
A little cleanup
Makefile: Update to valac-0.20; remove generated .c files on 'clean', too
Merge branch 'video-upload-error'
Revert "Implement basics of a "video test" option to not upload files that may not be supported by Gallery3"

This reverts commit 70391872d49a0240d90926dd44c6480e851d9b9f.
Doing this because I think the video-upload-error branch addresses the problem in a better way for the user.