RingtoetsPipingSurfaceLineCreateExtensionsTest.cs

* Implemented Create extension method for persisting PipingCalculationScenario instances. ** Extended create extension methods for RingtoetsPipingSurfaceLine, HydraulicBoundaryLocation, StochasticSoilModel and StochasticSoilProfile to take instance reuse into account. *** Updated PersistenceRegistry with Contains and Get methods accordingly. ** PipingCalculationScenario now implements IStorable. Related to Issue [WTI-472]
git-svn-id: https://repos.deltares.nl/repos/WettelijkToetsInstrumentarium/trunk@3468 5a3db67b-de53-47b5-99c8-a1c30a6650e2

Former-commit-id: e07f026ed5bf5ce70bc892070091348f08e3490c
Former-commit-id: c09556e107d7bd38a7d17af8faa7e6bad2b986eb