Master to develop

Closes #575, #626, and #642

See merge request funkwhale/funkwhale!495

Fix #642: Deploy documentation from the master branch instead of the develop branch to avoid inconsistencies

Correct URL to support forum.

See merge request funkwhale/funkwhale!491

Update docker.rst

See merge request funkwhale/funkwhale!477

Install wheel in the virtualenv

See merge request funkwhale/funkwhale!490

Resolve "UI for multi-disc albums"

Closes #631

See merge request funkwhale/funkwhale!488

Point to new gitlab URL

See merge request funkwhale/funkwhale!489

Resolve "Track position don't take care about disc number"

Closes #507

See merge request funkwhale/funkwhale!486

Fixed #621: None extension when downloading an in-place imported file

Closes #621

See merge request funkwhale/funkwhale!485

Fix #308: Licenses

Closes #308

See merge request funkwhale/funkwhale!481

Fix #608: Update Track.vue in order to use the correct search format on lyrics.wikia.com

Closes #608

See merge request funkwhale/funkwhale!483

Fix #626: Load env file in config/.env automatically to avoid sourcing it by hand

Closes #626

See merge request funkwhale/funkwhale!482

Fix #575: Documented which Subsonic endpoints are implemented

Closes #575

See merge request funkwhale/funkwhale!480