Provide new tutorial materials

[smk78]

We need to replace the dated and monolithic (SasView 2.x) Tutorial that presently ships with SasView 4.x with new materials that are fresh, engaging, and modern.

This is an umbrella ticket for this 'next generation' material, the development of which will be discussed and directed at

http://trac.sasview.org/wiki/TutorialsTNG

Several existing tickets relating to the provision of 'tutorials' are now captured on this wiki page and the corresponding tickets closed:

Closes #387 - Need new tutorial documentation
Closes #516 - Add Pr Tutorial module
Closes #517 - Add Invariant Tutorial Module
Closes #518 - Add 1D model fitting tutorial
Closes #519 - Add 2D model fitting Tutorial
Closes #520 - Add constrained fit Tutorial
Closes #521 - Add simultaneous fitting tutorial
Closes #522 - Add Batch Fitting Tutorial

Some of the 'next generation' material will require our SasView documentation build processes to produce PDF files. Tickets relevant to this are:

Refs #510 - Build PDF documentation along with HTML
Refs #927 - Add PanDoc to Build Servers

[butler]

Tutorials now just need to be written… one piece at a time. They will not get written for 4.2 (though some more pieces may?) so moving this ticket to 4.3 now.