rework property handling

+ DataType validators are shifted to __call__
+ as_json is moved to export_datatape()
+ new HasProperties Base Mixin for Modules/DataTypes
+ accessibles can be accessed via iterator of a module
+ properties are properly 'derived' and checked, are set with .setPropertyValue

remember: parameters only have properties, so use getPropertyValue()

Change-Id: Iae0273f971aacb00fe6bf05e6a4d24a6d1be881a
Reviewed-on: https://forge.frm2.tum.de/review/20635
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/lib/enum.py

@@ -289,7 +289,7 @@ class Enum(dict):
         return self[key]
 
     def __setattr__(self, key, value):
-        if self.name:
+        if self.name and key != 'name':
             raise TypeError('Enum %r can not be changed!' % self.name)
         super(Enum, self).__setattr__(key, value)