Auto-divide music by album

[NatoBoram]

Requires #179.

Sometimes, an album will have information that's incompatible with Pathephone, such as multiple artists for different files. Pathephone prevents the user from submitting his files without an "album artist". However, when there's none, entering false information is the only way out.

One way to solve this problem would be to separate files which contains incompatible information in different albums and queue them for review by the user before submitting them or auto-submit them all.

This would allow to dump a whole music library in the program, have it auto-divide everything in coherent albums, and have everything submitted automatically. Moar music = More fun!

[negamaxi]

@NatoBoram album artist field will be removed exactly because of the reasons you have described.