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/protocol/interface/tcp.py

@@ -141,10 +141,6 @@ class TCPRequestHandler(socketserver.BaseRequestHandler):
                         result = (ERRORPREFIX + msg[0], msg[1], [err.name, str(err),
                                                                  {'exception': formatException(),
                                                                   'traceback': formatExtendedStack()}])
-                    except ValueError as err:
-                        result = (ERRORPREFIX + msg[0], msg[1], [u"BadValue", str(err),
-                                                                 {'exception': formatException(),
-                                                                  'traceback': formatExtendedStack()}])
                     except Exception as err:
                         # create Error Obj instead
                         result = (ERRORPREFIX + msg[0], msg[1], ['InternalError', str(err),