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.

Allow to make connections directly based on VariableNetworkNodes. This is a first step, more changes have to be made in this direction.

Use the threaded version of the FanOut if a pushing feeder is distributed to multiple consumers, so all consumers receive updates immediately.

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.

Remove the restriction which prevented connecting nodes of the same direction. This was an artificial restriction, since later checks make sure that the network has exactly one feeder.

move the testTwoScalarPollPushAccessors into its own executable, which will contain all tests of illegal combinations

- all supported types
- check asynchronous behaviour
- check multiple consumers

- fixed a bug in the FanOut which did not wait for the trigger (since ProcessScalar::receive() does not wait)
- fixed a bug in Application::feedDeviceRegisterToControlSystem() not handling the last arugment (trigger) properly
- improved the output produced with VariableNetwork::dump()

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

do not delete the executable if the demoApp-xmlGenerator crashes when being executed from within the makfile

added also the consumer-type variables to the XML file

Add some first code to produce an XML file describing the application variables published to the control system. This is not yet doing anything useful for now...

start the synchronisation thread of the FanOut to "convert" a poll-type feeder into a pushing feeder by putting in an external trigger.