new poll mechanism

- remove secop.poller and basic poller
- regular polls for 'important' parameters done by method doPoll
- all other parameters are polled slower (slowInterval) and
  with lower priority (only one at a time when main poll is due)
- nopoll decorator for read_* to disable poll
- enablePoll attribute (default True) for disabling polling a module
- fast polls may be implemented by means of a statemachine
- configurable slow poll interval
+ allow a Parameter to override a Property (parameter
  Readable.pollinterval overrides Module.pollinterval)

Change-Id: Ib1b3453041a233678b7c4b4add22ac399670e447
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27832
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>

secop/core.py

@@ -33,8 +33,9 @@ from secop.lib.enum import Enum
 from secop.modules import Attached, Communicator, \
     Done, Drivable, Module, Readable, Writable
 from secop.params import Command, Parameter
-from secop.poller import AUTO, DYNAMIC, REGULAR, SLOW
 from secop.properties import Property
 from secop.proxy import Proxy, SecNode, proxy_class
 from secop.io import HasIO, StringIO, BytesIO, HasIodev  # TODO: remove HasIodev (legacy stuff)
 from secop.persistent import PersistentMixin, PersistentParam
+from secop.rwhandler import ReadHandler, WriteHandler, CommonReadHandler, \
+    CommonWriteHandler, nopoll