refs #7529 Generally fixes the issue with different Units

but more testing is necessary
refs #8794 Resolved conflicts while reverting ticket to master

Conflicts:
	Code/Mantid/Framework/MDAlgorithms/inc/MantidMDAlgorithms/ConvertToMDHelper2.h
	Code/Mantid/Framework/MDAlgorithms/src/ConvertToMD.cpp
	Code/Mantid/Framework/MDAlgorithms/src/ConvertToMDHelper2.cpp
refs #8794 mainly introducing monotonic ranges method in Units class

refs #7529 further enhancements (not finished)
refs #7529 Checkpoint, defining reduction limits
refs #7529 Finished limit for units and unit tests for these limits
refs #7529 removed unnecessary commits
Merge branch 'feature/8794_unitConversionLimits' into develop