To ISIS SANS add BACK/M1/TIME, BACK/M2/TIME, BACK/M1, etc

[Steve Williams]

From Richard Heenan

So we need a BACK/M1/TIME and a BACK/M4/TIME for SANS2d, in which 
case you might as well make BACK/M1 and BACK/M2 as well.

These should be read from the user settings file and treated in a similar way to BACK/MON/TIMES. However, BACK/MON/TIMES will affect monitor spectra 2 and 3 from the transmission workspaces, BACK/M1, spectrum 1, etc.

[Steve Williams]

(In [10729]) In the SANS user settings file BACK/M4/TIME followed by to numbers sets the background time for 4. Note that BACK/M3..., etc. are not implemented yet re #2664

[Steve Williams]

(In [11037]) The ISIS SANS background regions can now be set with settings commands like BACK/M?/TIME where ? is an number re #2664

[Steve Williams]

(In [11044]) In ISIS SANS a command like "BACK/MON/TIMES" or "BACK/M3" in the "user file" set the StartX and EndX arguments passed to Flatbackground re #2664

[Steve Williams]

The last comment should have contained "BACK/M3/TIMES or BACK/M3" for monitor 3 (replace 3 for any integer). The document for this is here http://www.mantidproject.org/SANS_User_File_Commands#BACK

[Michael Reuter]

The changes to the code look like they are doing what was requested in the ticket.

[Stuart Campbell]

This ticket has been transferred to github issue ​3511