removed old style syntax

- removed secop/metaclass.py
- moved code from ModuleMeta to modules.HasAccessibles.__init_subclass__
- reworked properties:
  assignment obj.property = value now always allowed
- reworked Parameters and Command to be true descriptors
- Command must now be solely used as decorator
- renamed 'usercommand' to 'Command'
- command methods no longer start with 'do_'
- reworked mechanism to determine accessible order:
  the attribute paramOrder, if given, determines order of accessibles
+ fixed some issues makeing the IDE more happy
+ simplified code for StatusType and added a test for it

Change-Id: I8045cf38ee6f4d4862428272df0b12a7c8abaca7
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/25049
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

doc/source/reference.rst

@@ -20,13 +20,12 @@ Parameters, Commands and Properties
 ...................................
 
 .. autoclass:: secop.params.Parameter
-.. autoclass:: secop.params.usercommand
+.. autoclass:: secop.params.Command
 .. autoclass:: secop.properties.Property
 .. autoclass:: secop.modules.Attached
     :show-inheritance:
 
 
-
 Datatypes
 .........