implement the "testable mode" in which the application can be paused and resumed by the test routine

Added a TestDecoratorRegisterAccessor which is optionally put around accessors to facilitate test of applications. This TestDecoratorRegisterAccessor does not yet do anything, functionality will be added in the next commits.

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.

fixed a bug in the test: a module was defined at the same scope as the application, which lead to crashes when terminating the application sometimes
(same as last commit, but for a different test)

fixed a bug in the test: a module was defined at the same scope as the application, which lead to crashes when terminating the application sometimes

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

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

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

Adapation to the unified versions of ControlSystemAdapter and DeviceAccess.

Status: Library compiles, tests do not yet compile.

Refactored the tests so that all modules are inside the application classes. Otherwise the shutdown scheme might break at some point.

- extended the trigger tests
- removed some debug output

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

move the device test out of the AppModuleConnections test into its own executable and split it into a feeding and a consuming part

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.