improve handling of module init methods

- complain when super call is omitted (this is a common programming
  error in Mixins)
- redesign waiting mechanism for startup

+ rename MultiEvent method 'setfunc' to 'get_trigger'

Change-Id: Ica27a75597321f2571a604a7a55448cffb1bec5e
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27369
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop_demo/modules.py

@@ -133,6 +133,7 @@ class MagneticField(Drivable):
     status = Parameter(datatype=TupleOf(EnumType(Status), StringType()))
 
     def initModule(self):
+        super().initModule()
         self._state = Enum('state', idle=1, switch_on=2, switch_off=3, ramp=4).idle
         self._heatswitch = self.DISPATCHER.get_module(self.heatswitch)
         _thread = threading.Thread(target=self._thread)
@@ -235,6 +236,7 @@ class SampleTemp(Drivable):
                      )
 
     def initModule(self):
+        super().initModule()
         _thread = threading.Thread(target=self._thread)
         _thread.daemon = True
         _thread.start()