PipingOutput not deletable by using <delete> in tree. Made PipingFailureMechanism observerable. Added validate context menu item on PipingDataNodePresenter. Implemented Validate routine in PipingCalculationService. Added PipingCalculationResult for different possibilities of results. Added TestPipingOutput which can be used for simple testing. Made PipingCalculationService responsible for its own logging. Moved resources related to logging of PipingCalculationService to Wti.Service project. Related to Issue [WTI-18]