Merge remote-tracking branch 'origin/feature/4841_params_from_py_to_IDF'
Merge remote-tracking branch 'origin/feature/7998_larmor_idf'
Re #7768. Add d-spacing as an available filtering unit.

Garrett says that this is the one he would use most often.
Re #7768. Ensure selected variable doesn't get forgotten.

Previously, even if the user had chosen something else it would revert
to scan_index if the dataset was being filtered.
Merge remote branch 'origin/defect/5872_SliceMDInterupt'
Merge remote-tracking branch 'origin/feature/7923_DGS_comment'
Merge remote-tracking branch 'origin/feature/8034_combinemulti_stitch1d'
Merge remote branch 'origin/feature/7950_pyqt_v2_api_for_qstring_qvariant'
Merge remote-tracking branch 'origin/feature/7652_process_bkgd'
Merge branch 'master' of https://github.com/mantidproject/mantid
Merge remote-tracking branch 'origin/bugfix/8076_dgsdiagnose_diagspectra_handling'
Merge remote-tracking branch 'origin/bugfix/8080_logging_broken_clean_install'
Correct the LoadISISNexus2 to load instrument defined in nxs

re #8083
Merge branch 'bugfix/8083_load_instrument_inside_nexus' into develop