Provide User Guide

[jreadey]

Provide end-user guide. (via ReadTheDocs?). Link to Help menu item.

[giumas]

About documentation, I believe that:

• the content of the 'docs' folder is outdated: https://github.com/HDFGroup/hdf-compass/blob/develop/docs/index.rst
• the documentation should be unified (with the "Compass model" as a chapter/section). Looking at the conf.py I can read "HDFCompass Data Model". So I would substitute it with a mode generic "HDF Compass"
• it is missing a make.bat for Windows user (there is only the Makefile: https://github.com/HDFGroup/hdf-compass/blob/develop/docs/Makefile)

[giumas]

This is a possible structure for the manual: http://giumas-hdf-compass.readthedocs.org/en/latest/

[jreadey]

User guide should mention the key-bindings for navigation (#101)