refs #6667 modifying system tests to work with new dgreduce

in ISIS
refs #6667 Added dgreducer based system test for MAPS
refs #6667 minor changes

mainly related to ongoing work on other branches
refs #6667 MAPS system test modified to work hopefully right

and produce correct WB cross-section if set up this way (currently it is not and runs against some run data)
refs #6667 Modified MAPS and MARI System tests pass

one more workflow test has been added for MARI
refs #6667 System tests modified to work for dgreduce.
refs #6667 Added missing file needed for MAPS reduction
refs #6667 Fixed DirectInelasticDiagnostic and LoadLotsOfFiles

hopefully
refs #6667 Should fix mysterious error in MARI sum test
refs #6667 Some key-words corresponding to Parameters file
refs #6667 guessed last parameters providing difference

in DirectInelasticDiagnostic2
refs #6667 Should fix issue when arb units requested files

necessary for abs units only
Merge remote-tracking branch 'origin/feature/6667_ISISReductionInMantid'