Fixed ThrowIfArgumentNull to give proper message. Fixed use of message CsvHeaderNullOrEmpty (it was not found because name was different). Improved tests to see if expected message was given for header and splitter. Related to Issue [MWDAM-1556]
Cleanup code due to SonarCube analysis - Use ArgumentNullException i.s.o. NullReferenceException (implement ThrowHelper) - Move strings to resources Related to Issue [MWDAM-1556]