ReadHandler and WriteHandler decorators

modules with a couple of parameters with similar read_* or
write_* methods may handle them by generic methods wrapped
with decorators ReadHandler / WriteHandler

The trinamic driver is included in this change for demonstrating
how it works.

In a further step, the special handling for the iohandler stuff can
be moved away from secop.server and secop.params, using this feature.

+ fix problem on startup of trinamic driver (needs MultiEvent.queue)
+ some other small fixes
+ apply recommended functools.wraps for wrapping

Change-Id: Ibfeff9209f53c47194628463466cee28366e17ac
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/27460
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>

secop_psi/ppms.py

@@ -320,7 +320,7 @@ class Chamber(PpmsBase, Drivable):
         general_failure=15,
     )
 
-    value = Parameter(description='chamber state', handler=chamber,
+    value = Parameter(description='chamber state',  # handler=chamber,
                       datatype=EnumType(StatusCode))
     target = Parameter(description='chamber command', handler=chamber,
                        datatype=EnumType(Operation))
@@ -482,7 +482,7 @@ class Temp(PpmsBase, Drivable):
         if workingramp != 2 or not self._ramp_at_limit:
             self.log.debug('read back ramp %g %r' % (workingramp, self._ramp_at_limit))
             self.ramp = workingramp
-        result = dict(setpoint=setpoint, workingramp=workingramp)
+        result = dict(setpoint=setpoint, workingramp=workingramp, approachmode=approachmode)
         self.log.debug('analyze_temp %r %r' % (result, (self.target, self.ramp)))
         return result