Support more video formats

This pull request adds support for video files with the files endings .wmv, .asf and .ogv. The respective container formats are already supported, but we did not support specific video file extensions for ASF and Ogg. This supplements our already existing support for .m4v and .oggtheora files.

This was tested with local .wmv and .ogv files and some test files from http://www.creatoon.com/samples.php.

Background to this is that I have started to rip and tag music video DVDs and also tagging various video files that I got from data tracks of some CDs I purchased.