added function to obtain list of accessors from modules recursively (i.e. including accessors from sub-modules)

Added names and owners for modules, to build a full hierarchy chain. The syntax for creating modules is now not so nice, a better way has to be found (maybe by adding a macro if better solution can be found).

Read all application inputs once before starting the module threads, so the initial values are correctly present.

For this purpose, additional changes were necessary:
- Added support for constant values as feeders and consumers (just ignore the writes)
- Connect all unconnected application accessors to constants after defining the connections and before creating the implementations
- Renamed the user-overridden function "initialise()" into "defineConnections()", since more actions are now necessary during initialise().
- The connections are now made (i.e. the implementations are created) during the initialisation phase

moved VariableNetworkNode member to AccessorBase class, so the network node information can be accessed also when having only the pointer to the base class

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

- fixed copying only the first element in some situations

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

partial fix for problems due to moving to new ControlSystemAdapter structure: allocate and use the buffer from the NDRegisterAccessor
tests still do not pass

Adapation to the unified versions of ControlSystemAdapter and DeviceAccess.

Status: Library compiles, tests do not yet compile.

- extended the trigger tests
- removed some debug output

Introduced the DeviceModule class which provides an interface to obtain VariableNetworkNodes for device registers

- performed some code cleaning and refactoring
- store all nodes in a VariableNetwork in a single list, to allow deciding later if a node is feeding or consuming

This commit is an intermediate commit and has known bugs. Almost all tests are failing and the demoApp is not running. Debugging will be done in a next step.

introduced an operator>> and operator<< syntax to connect network nodes. to realise this, the VariableNetworkNode class has been changed into a pimpl pattern.