Fixed setting of the master engine when assigning a SlaveActivity to an ExecutionEngine

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
tests: added slave_test to test operation calls between components running in a SlaveActivity

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
ExecutionEngine: do not forward waitForMessagesInternal() and waitAndProcessMessages() calls to master engine

waitForMessagesInternal() is also used by waitForFunctions() and thus would wait for the wrong condition variable.
Forwarding waitForMessages() to the master should be sufficient for processing operations in slave engines.

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
ExecutionEngine: moved message forwarding to master to the top of ExecutionEngine::process()

The forwarding does not require that the slave engine has an activity.

Signed-off-by: Johannes Meyer <johannes@intermodalics.eu>
Merge pull request #71 from meyerj/slave-activity-fixes

Finally fixing the SlaveActivity message processing