Draft: Ported condition test of TimeHeadway

• Ported TimeHeadwayConditionTest from existing_open_scenario_engine/test/TimeHeadwayConditionTest.cpp to the generated engine
• Some tests had to be adapted for the time being, since the generated engine doesn't implement the checking of preconditions
  • Instead the generated engine either does nothing specific or throws an exception in case some preconditions are not met
• Note: This merge request is intentionally small, so that I can get used to the processes surrounding this repo