added preliminary support for tags to application variables which can be searched for and used to generate virtual modules

fixed replacing Array and ScalarAccessors, which was broken after moving to the NDRegisterAccessorBridge-based accessors

fixed poll-type inputs using no longer non-blocking read after the switch to the NDRegisterAccessorBridge-based accessors

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

Removed the macros for defining accessors and introduced convenience classes instead. This adds slightly more syntactic sugar, but also allows more flexibility and seems to be a more coherent interface.

This commit incompatibly breaks the interface with the previous versions. Since ApplicationCore is not yet used in any productive environment, no compatibility is provided.

- Default constructor for Accessor exists now
- A function Accessor::replace() allows to assign a new accessor
- For clarity/safety: copying accessors using the assignment operator is now forbidden
- The destructor of the accessor unregisters it from the module (to allow temporary accessors)

Added description field to the variables. It is currently ignored and will be added to the XML file in a next step.

- extended the trigger tests
- removed some debug output

Split the SCALAR_ACCESSOR macro into SCALAR_OUTPUT and SCALAR_INPUT to prevent output accessors to be created in poll mode (which makes no sense). Since some tests were using this, now instead a DeviceAccessor in poll mode is used for these tests.

removed a function declaration which was not implemented and cannot be implemented right now (missing feature in the CSA)

improved structure of network creation and added a FanOut to distribute values to multiple consumers

This is a first mock implementation with very limited functionality. The idea is based on discussions during the OPC-UA control system adapter kickoff meeting and subsequent personal discussions.