simplify configuration of IO modules

As the communicator class needed for a module can be specified,
in the configuration we do not need to specifiy it explicitly.

A new configurator function IO() is introduced for this, defining
names and uri only.

- update also configuration reference and a tutorial example
- update get_class function to accept attributes of classes like
  'frappy_demo.lakshore.TemperatureSensor.ioClass' and import from
  modules other than frappy... like 'test.test_iocfg.Mod'.
- add ioClass to the example class for the temperature controller
  tutorial

Change-Id: I3115371d612f14024e43bc6d38b642e1d27b314d
Reviewed-on: https://forge.frm2.tum.de/review/c/secop/frappy/+/38071
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

.pylintrc

@@ -86,7 +86,7 @@ dummy-variables-rgx=_|dummy
 
 # List of additional names supposed to be defined in builtins. Remember that
 # you should avoid to define new builtins when possible.
-additional-builtins=Node,Mod,Param,Command,Group
+additional-builtins=Node,Mod,Param,Command,Group,IO
 
 
 [BASIC]