Merge branch 'feature/7263_improve_load_selection_performance' into develop

Refs #7263
Conflicts:
	Code/Mantid/Framework/DataHandling/inc/MantidDataHandling/LoadILL.h
	Code/Mantid/Framework/DataHandling/src/LoadEventNexus.cpp
	Code/Mantid/Framework/DataHandling/src/LoadILL.cpp
	Code/Mantid/Framework/DataHandling/src/LoadSassena.cpp
Temp move LoadILLSANS to new loader hierachy on develop. Refs #7263