Enhance help (non model) documentation

[smk78]

The Sphinx help docs for Release 3.1 represent a porting of the pre-
existing HTML help docs to ReSTructured text.

Some restructuring has been conducted. Some (obvious!) equation errors
have been corrected. Some 'missing' content has been added.

The next steps are:

• checking that the documentation actually reflects the current functionality of the program!

• updating existing screenshots to match the current functionality of the program

• adding additional screenshots

NOTE: Model documentation review is addressed separately in Ticket #19.

[smk78]

Also consider, as suggested by Richard, doing away with the 'top level' documentation menu. This would mean moving the links to the Model Functions and the Developer Documentation from Sphinx index.rst to the GUI Help dropdown and reorganising lower toctrees.

[smk78]

Last suggestion dealt with under Ticket #436

[smk78]

Need to add something about using Save Analysis and Save Project (suggestion ported from Ticket #20).

[smk78]

Also see Ticket #33.

[butler]

While some work has been done, we still need an organized start to finish review which is clearly not going to be able to be done in time for release 4.0. Moving this to +1 but keeping the high priority on it.

[smk78]

After discussions between PaulB & Steve we are closing this ticket as its original intention has now been served. A LOT of good work on the documentation has taken place since Code Camp III and it is now in a far better place than it was, but there will ALWAYS be room for improvement. If there are specific documentation issues/enhancements they should now be noted in specific tickets.