add test for findTag() (was never really tested before), including advanced features like HierarchyModifier::moveToRoot

- added more comments
- need to catch exception by reference, else the message seems to be lost
- test if the message is correct
- test if device is really closed and opened again
- changed names of status variables in control system to match the general naming conventions

connect the deviceError module with the control system - otherwise it crashes due to an unconnected variable

- use latest backend factory interface and the CDD
- changed code formatting

- treat the two directions of bidirectional variables properly in testable mode (i.e. as individual variables with each one counter)
- fix a data race in testable mode in case a bidirectional variable rejected a value (was not holding a required lock)

extend test of bidirectional variables to include plain direct Application to ControlSystem connections (no FanOut etc. involved)

extended the test to make sure also the "observer" variables in the control system show the right values

- implement ThreadedFanOut version with return channel
- add test for ThreadedFanOut with return channel

bidirectional variables: pass on version numbers in modules from the last blocking read on to any write operations, to resolve conflicts of concurrent variable updates properly

Implemented bidirectional process variables for control system variables. There are still bugs and the test is failing...

Added preliminary support for bidirectional variables. There are still some known issues, e.g. concurrent updates can still lead to race conditions. This will be addressed soon.

Now one can add ScalarOutput and ArrayOutput variables to the history modules by using tags.