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.

Intermediate commit before the weekend: added options to add an external trigger to a network to handle poll and push properly. Currently it does not work properly.

renamed publishDeviceReadRegister() and publishDeviceWriteRegister() into feedDeviceRegisterToControlSystem() and consumeDeviceRegisterFromControlSystem()

renamed publish() and connectToDevice() into more specific feedToControlSystem()/consumeFromControlSyste() and feedToDevice()/consumeFromDevice()

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

Introduced the VariableNetwork describing the connections of variables/accessors before things get actually instantiated. This is needed to generate an XML file containing the published variables based on that information.

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.