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

several things: critical socket threading bug from comba resolved. adapted interfaces to pv / tank / database

implemented manual inserting of a ScheduleEntry. Manual radio control is not far away. Found a - at least for me - hard to track bug coming from sqlalchemy session. not fixed

code quality enhanced, timer management improved, started to implement methods for manual playlist editing