Allow specifiacation of the other SANS transmission detector.

[Steve Williams]

In ISIS SANS runs the transmission is calculated from the number of neutrons reaching the a post-sample monitor (normally detector ID = spectrum = 3) and the pre-sample (normaliation) monitor (normally 2).

The pre-sample monitor is specified in the user file with MON/TRANS/SPECTRUM=? and can be overriden in the monitors section of the Analysis Details tab of the SANS GUI.

Todo: The post-sample monitor will be specfied with TRANS/TRANSPEC=? in the user file and overriden by a box on the GUI similar to above. There will be documentation inhttp://www.mantidproject.org/SANS_User_File_Commands and http://www.mantidproject.org/Using_the_SANS_GUI .

[Steve Williams]

If not set this value is left at default-transmission-monitor-spectrum from the parameters xml file.

[Steve Williams]

(In [10680]) The SANS user file now parses TRANS/TRANSPEC for use in the transmission calculation re #2758

[Steve Williams]

(In [10695]) The SANS transmission calculation can be performed with any combination of monitors re #2758

[Steve Williams]

(In [10733]) The SANS fix bug with log fit setting not making it to the GUI re #2758

[Steve Williams]

(In [10751]) Allow the SANS full range transmission ranges to be changed re #2758

[Steve Williams]

The new user commands have been set up and work as in http://www.mantidproject.org/SANS_User_File_Commands The GUI additions now have lower priority and are in ticket #3176

[Mathieu Doucet]

Everything seems to be there. Checked that the monitor IDs are passed properly when calling CalculateTranmission.

[Stuart Campbell]

This ticket has been transferred to github issue ​3605