Refs #6688  Elim Convert2DiffMD and elim equality tests for row,col of peak

A system test on master at isis failed because the ConvertToDiffractionMD gives random results for the
center of the peak.  This method is replaced by ConvertToMD, which does not give random results, and testing
for peak equality will not require equality of row and column numbers.
Merge branch 'bugfix/6277_try' into develop