TS: transplanted PeriodicCall into Meresco Components, refactoring imminent.
TS: Refactored Schedule comparison and hashing.

Removed __cmp__, only added __eq__ and __ne__; since sorting Schedule
objects is not relevant yet.
TS: absorbed more functionality from PeriodicDownload
HM/TS: bugfix Schedule for period=0
TS/HM: InitialSchedule; Error logging; getState; setSchedule
HM/TS: removed TODO.