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

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

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

started to implement trackservice. removed unused (comba)methods from scheduler.py&calender.py. minor beautyness improvements

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