Add WorkspaceIndex attribute in InelasticDiffSphere and InelasticDiffRotDiscreteCircle

[DanNixon]

Fixes #11447.

To test:

• Load irs26176_graphite002_red.nxs
• Run the following script with the log set to debug and notice there is log output showing the value of Q used for each spectrum, this value should be equal to that shown in Show Detectors
• Add the Q parameter in (add ,Q=1.2 after the Shift parameter), run again, notice now the same Q value is used for all spectra (as was done before).
• Do the same again but change the function to InelasticDiffRotDiscreteCircle

PlotPeakByLogValue(
    Input='irs26176_graphite002_red,i0;irs26176_graphite002_red,i1;irs26176_graphite002_red,i2;irs26176_graphite002_red,i3;irs26176_graphite002_red,i4;irs26176_graphite002_red,i5;irs26176_graphite002_red,i6;irs26176_graphite002_red,i7;irs26176_graphite002_red,i8;irs26176_graphite002_red,i9',
    OutputWorkspace='fit',
    Function='name=InelasticDiffSphere,Intensity=1,Radius=2,Diffusion=0.1,Shift=0'',
    FitType='Individual',
    PassWSIndexToFunction=True,
    CreateOutput=True,
    OutputCompositeMembers=True)

[mantid-roman]

• There is no unit test for the new functionality.
• Attribute Q should be a double. You should be able to do: getAttribute("Q").asDouble()

[DanNixon]

@mantid-roman Is there any way to have a double attribute that can be left blank?
That is the only reason I have not done this.

[mantid-roman]

You can use either EMPTY_DBL() for Q or EMPTY_INT() for WorkspaceIndex as we do in algorithms.