moved exception handling documentation into its own dox file and added documentation about DataValidity flag propagation

changed: device is not intialized in constructor anymore.

Test still does not work.
-Unable to get the exception status for the device throwing exception.
-Second device only works it has it's own trigger.

- add test for full exception handling

  DeviceModule and ControlSystemModule now do not take the optional prefix argument in their constructors any more. Use the [] operator instead to get the submodule.

- Add ExceptionHandlingDecorator and decorate all device variables with it.

- 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

Proper implementation of move constructors and move assignment operators for all module types (including tests for the assignment operator)

fixed connectTo() so it now uses the dynamic/virtual model and thus obeys e.g. eliminated hierarchies etc.

Fixed some more problems with the move sematics of EntityOwner/Module. Re-registration at the owner was missing and some things were done in the wrong place. Also the move assignment is now back again.

put the move constructor and move assignment-operator into the EntitiOwner base-class and inherit them

also make sure for DeviceModules to always return the same sub-module with the [] operator when passing the same sub-module name

Instead of making the DeviceModule return the same VariableNetworkNode for the same register, an optimisation step before realising the connections (but after all connections have been defined) is performed. In this step, all networks sharing the same (device-type) feeder will be merged. This is more flexible and avoids problems with (potentially different) triggers etc.

A DeviceModule now returns the same VariableNetworkNode when asked for the same register multiple times. This leads to a new restriction that registers can now only be either read or written. This restriction can be mitigated by using the logical name mapper to create an alias of the register. This has been implemented for the tests and the demo application.

Changed Module::connectTo() to accept also temporary module objects, e.g. as returned by findTag(). As a consequence, the operators [] and () of the modules had to be changed to const.

Rebased the ScalarAccessor and ArrayAccessor classes onto the mtca4u::NDRegisterAccessorBridge class.
Known problems present: code compiles but tests do not run

Forward declaration is taken from DeviceAccess header file, which solves problems if classes are moved to another namespace.

allow specifying the array length for direct connections between device and control system (as the type is already defined in this case)