re #1538 - fixed some issues with load algorithms

Code/Mantid/DataHandling/src/LoadGSS.cpp

Code/Mantid/DataHandling/src/LoadRKH.cpp

Code/Mantid/DataHandling/src/LoadRawHelper.cpp

Code/Mantid/Nexus/src/LoadISISNexus2.cpp

Code/Mantid/Nexus/src/LoadMuonNexus2.cpp

Code/Mantid/Nexus/src/LoadNexusProcessed.cpp

Code/Mantid/Nexus/src/LoadSNSNexus.cpp