this is a simplicifcation for the ppms driver
- the derivation of a changecmd from a querycmd is moved to
CmdHandler.__init__
- the special treatment of handlers when writing configured
parameters has moved to CmdHandler.write
- introduced Drivable.isDriving, changed Module.isBusy
Change-Id: I8862ecda9c8cc998bb018bd960f31c9488146707
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22033
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>