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>

secop/metaclass.py

@@ -119,7 +119,6 @@ class ModuleMeta(PropertyMeta):
                                            "and read_%s" % (pname, pname))
                 rfunc = handler
             else:
-                rfunc = attrs.get('read_' + pname, None)
                 for base in bases:
                     if rfunc is not None:
                         break