Resolve ""Play Now" button doesn't queue properly"

Closes #632

See merge request funkwhale/funkwhale!498

Removed duplicated susbsonic tests

See merge request funkwhale/funkwhale!497

Fix #578: iframe embed

Closes #578

See merge request funkwhale/funkwhale!496

We were testing both xml and json rendering for every view but this takes a very long time, so we only do json for most views now.

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