Refs #8550. Initial files for MuonGroupDetectors.
Refs #8550. MuonGroupDetectors: code to apply grouping.

Plus some tests for it.
Refs #8550. Use new functionality in PlotAsymmetryByLogValue.
Refs #8550. Remove unused ApplyGroupingFromMuonNexus.
Merge branch 'feature/8550_muon_tidy_up_grouping' into develop