Create Unit Tests for GetNegMuMuonicXRD algorithm

Engg: implement first GUI

On pull request builds this should force all doc tests to run.

Removed use of OutputVertexes for ConvertSpectrumAxis

Fix SimulatedDensityOfStates doc test

Removed the type that set output vertexes value in the
convertSpectrumAxis algorithm

Refs #13482

Refactoring of DNS algorithms

The final write of the GSAS calibration file would fail on windows if the output folder is a network share like \\olympic\babylon because of multiple double back-slashes being inserted - and some of them misinterpreted as escape sequences.

Sum characterizations in SNSPowderReduction. All tests are passed.  Pull request is then closed. 

Output 2D workspace before Re-gridding step in ConvertToReflectometryQ

Enables detector table to be generated from python

Improvements to SimulatedDensityOfStates

Refs #13432

Allow AppendSpectra to append multiple times

Add diagram for MolDyn

ISIS powder diffraction scripts

13368 implement quadratic scaling for color fill plots

Refs #13405

Refs #13405

Introduce MDFrame and MDUnits

Set axis to something Mantid understands better in nMoldyn 4 loader

FilterEvents Interface Issues

Refs #13262