Change ISIS user file to python or other format

[NickDraper]

The 'user file' is a term used by the ISIS SANS group to an input 'parameter file' users can edit and which drives data reduction.

This change is partially technically driven to switch to format easier to maintain.

New format to consider includes JSON, YAML and Python dictonary.

Need to maintain backward compatability.

Contact: Steve King

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Keywords: SSC, 2015, RAL, sansUI

[NickDraper]

@NickDraper (2015-03-10T15:49:02):
Batch modify all SSC tickets to critical priority (this will also show up as an update for all those already as critical)

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@Anders-Markvardsen (2015-03-18T16:26:41):
Peter, just to make you aware that there was this longer term 2015 SSC requirement output

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@PeterParker (2015-04-21T12:33:16):
In today's catchup session with the SANS group, Richard suggested that it might be a good idea for him to first explore what some of the python commands might look like and the SANS group may want them to work. We would then take a look at what he comes up with and discuss further.

[AntonPiccardoSelg]

This is an issue which is brought to my attention quite often by the SANS scientists.
Recently Reflectometry scientists have expressed the need for user files.

This would be a good opportunity to unify our approach.

[gemmaguest]

Duplicate of #18826