Implement more subsonic endpoints

See merge request funkwhale/funkwhale!457

Fix #573: Added "type: funkwhale" and "funkwhale-version" in Subsonic responses

Closes #573

See merge request funkwhale/funkwhale!456

Fixed #581: missing track count on various library cards

Closes #581

See merge request funkwhale/funkwhale!455

Fix #585: Now start radios immediatly, skipping any existing tracks in queue

Closes #585

See merge request funkwhale/funkwhale!454

Fix #576: Improved keyboard accessibility on player, queue and various controls

Closes #576

See merge request funkwhale/funkwhale!453

Fix # #562: Document how to find and use library id when importing files in CLI

Closes #562

See merge request funkwhale/funkwhale!452

Use most recent image from develop as build cache

See merge request funkwhale/funkwhale!451

Fix #422: Do not display "view on MusicBrainz" button if we miss the mbid

Closes #422

See merge request funkwhale/funkwhale!450

Fix #470: Properly encode Wikipedia and lyrics search urls

Closes #470

See merge request funkwhale/funkwhale!449

Fix 0.17 upgrade instructions.

See merge request funkwhale/funkwhale!448

Make them consistent with general upgrade instructions.

fix some links and typo

See merge request funkwhale/funkwhale!447

Fix some typos and improve language in the federation documentation

See merge request funkwhale/funkwhale!445

Revise discussion of import methods and improve wording

See merge request funkwhale/funkwhale!444