reactivated fallback and callback from lqs, fixed multiple lineins on engine level, having the problem that fallback does not start

checking free diskspace. send warnings (email & logging) and stop recorder if a critical value is reached.

found stupid bug in fetching programme from pv. added more or less random playlists. almost reactivated whole chain from fetching to liquidsoap

got too many data from pv. data is now filtered => easier debugging. now it is only possible to comment this to disable this function

enabled API call for liquidsoap state (enabled & connected streams, enabled & recording recorder, enabled lineins and enabled lineouts)

5 different recorders possible. 'last' missing thing on liquidsoap side: smooth transition between mixer.selects

recording is now part of engine.liq. a redefinition of the recorded source is needed if those two should be separated.

Origin/aura into master

See merge request autoradio/engine!2

This reverts commit 62a8c7ba, reversing
changes made to a9c94736.

# Conflicts:
#   libraries/database/broadcasts.py
#   libraries/security/user.py
#   libraries/security/whitelist.py