Moved StructureIdEqualityComparer to separate file, since it was defined twice. Can be moved to *Ringtoets.Common.* if used by other structures Extended tests of TestStructure Related to Issue [WTI-1175]
Made log protected in FileImporterBase so that it does not need to be redefined in every derived class. Added ImporterMessageProvider to HeightStructuresImporter Related to Issue [WTI-1172]