refs #8614 Attempt to remove part of generic code out of LET test
refs #8614 new system test for recent LET
refs #8614 Minimal set of changes to LET system test

Here are the changes to system test caused by GIT refusing to accept large raw file. I use existing raw wb file (though the data would be physically incorrect) and need to modify the reference results. As the results are physically incorrect, I am trying to make minor data set relating to the existing one and still testing the reduction
refs #8614 Changes to stresstesting allowing checkin mutlirep

and ISISDirectInelastic working with old raw/map/mask files
refs #8614 data files for event multirep mode
refs #8614 modified reference result files

using old mask map and det.dat file
Merge branch 'bugfix/8614_letReduction' into develop