write configured parameters to the hardware

writable parameters with a configured value should call write_<param>
on initialization.
+ introduced 'initwrite' parameter property for more fine control over this
+ minor improvements in metaclass.py, param.py, commandhandler.py
+ rearranged test_modules.py

Change-Id: I2eec45da40947a73d9c180f0f146eb62efbda2b3
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/21986
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

test/test_poller.py

@@ -157,9 +157,11 @@ class Module:
     def isBusy(self):
         return self.is_busy
 
-    def pollOne(self, pname):
+    def pollOneParam(self, pname):
         getattr(self, 'read_' + pname)()
 
+    writeOrPoll = pollOneParam
+
     def __repr__(self):
         rdict = self.__dict__.copy()
         rdict.pop('parameters')