accept module properties without leading '.' in config files

as module properties and parameters anyway share the same namespace,
there is no need to distinguish in config files.

+ a parameter default value may be overriden just with a class
  attribute.

Both improvements help to switch between parameters and properties
more easily.

Change-Id: Ieb5cf3121f37c7c04e63345d3e95dfaf42726455
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22054
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/metaclass.py

@@ -25,7 +25,7 @@
 import time
 from collections import OrderedDict
 
-from secop.errors import ProgrammingError
+from secop.errors import ProgrammingError, BadValueError
 from secop.params import Command, Override, Parameter
 from secop.datatypes import EnumType
 from secop.properties import PropertyMeta
@@ -103,6 +103,16 @@ class ModuleMeta(PropertyMeta):
         # 2) for the describing message
         newtype.accessibles = OrderedDict(sorted(accessibles.items(), key=lambda item: item[1].ctr))
 
+        # check for attributes overriding parameter values
+        for pname, pobj in newtype.accessibles.items():
+            if pname in attrs:
+                try:
+                    value = pobj.datatype(attrs[pname])
+                except BadValueError:
+                    raise ProgrammingError('parameter %s can not be set to %r'
+                                            % (pname, attrs[pname]))
+                newtype.accessibles[pname] = Override(default=value).apply(pobj)
+
         # check validity of Parameter entries
         for pname, pobj in newtype.accessibles.items():
             # XXX: create getters for the units of params ??