Fix Units on ConvertMDHistoToMatrixWorkspace

[OwenArnold]

This ticket is blocks : TRAC8992

The following illustrates the problem.

#!python
CreateMDWorkspace(Dimensions='2',EventType='MDEvent',Extents='-10,10,-10,10',Names='Q_lab_x,Q_lab_y',Units='A,B',OutputWorkspace='test')
FakeMDEventData(InputWorkspace='test',UniformParams='1000',PeakParams='100000,0,0,1')
# Create a line cut
line_md = BinMD(InputWorkspace='test',AxisAligned='0',BasisVector0='X,units,0.888154,0.459545',BasisVector1='Y,units,-0.459545,0.888154',Translation='-4.93562,-2.3918',OutputExtents='0,9.61632,-0.1,0.1',OutputBins='100,1')
line_2d = ConvertMDHistoToMatrixWorkspace(line_md)
plotMD(line_md)
plotSpectrum(line_2d, 0)

These plots should be equivalent, but the X-units are wrong in the line_2d cut. This is because the Convert algorithm isn't properly sourcing the coordinate transformations. The default should be that it does. An optional parameter expressing the need to preserve the existing behaviour would be desirable.

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Keywords: PatchCandidate

[OwenArnold]

This issue was originally trac ticket 9009