SaveNexusESS

Update Facilities.xml

The spline interpolation gives slightly different values in the noisy sections of the data at the ends.

Update script repository endpoints to https

The server has handled https for some time now.

Remove seeAlso list containing only an empty string

Also provide documentation for new version

This is means that if we introduce any problems into new
LoadNexusProcessed, it will be easy to move back to version 1.

Add CHESS and ZEEMANS instruments to SNS

These are proposed second target station instruments. Adding them to
`Facilities.xml` makes it significantly easier to process various
simulated data files through mantid.

Removes a warning from the help build.

I overlooked that instrument will save a physical_detector and
physical_monitor in cases of being able to access detectorIds

GPSANS: correct translation equation along X-axis