Part 2: Bug 947816 - Add metadata test for VorbisComment (.ogg) and AAC (.m4a)

Rename id3_test to metadata_test because that's what it is.
Bug 947816 - Part 3: added id3 v1 test. Including v1+v2 sample.
Bug 796305 - Part 1: Extract disc number from ID3 and MP4.

Modify id3v2.3 and mp4 test file to include that metadata.