Add support for album art

[mr-smidge]

The library does not currently support album art: tracks are created with no album art set.

The format in the AlbumArt table involves the following columns:

• albumArt - a binary blob (the PNG/JPG data
• hash - unsure exactly how the hash is derived

[DeathCamel58]

The hash is SHA1 with some sort of prior modification. The current release binaries are all obfuscated, which makes it a pain to decipher. Engine OS 2.0.1's /usr/Engine/Engine binary isn't obfuscated though. Looks like librarian::Track::calculateHashForAlbumArt is a good place to start the search in that binary.

Also, we don't really have to know how the hash column is computed, as id and albumArt are enough to get the album art images to display properly in Engine OS (tested on 4.0.1).