* Reworked module file tutorial section
First draft for the SC17 update. This includes:
- adding an introduction on module files + Spack's module
generation blueprints
- adding a set-up section and provide a docker image for easy set-up
- updating all the relevant snippets
- extending a bit some of the concepts that were already touched
* Added reference to #5582 + committed Dockerfiles
Also fixed a couple of typos spotted by Denis.
* module file tutorial: added section on template customization
* module file tutorial: fixed minor typos + rephrased a sentence
* module file tutorial: made explicit that Docker image comes with software
* module file tutorial: improved phrasing and layout.
Thanks Hartzell!
* module file tutorial: added vim and nano to editors
* module file tutorial: fixed typo
* Fixed typos
Thanks Adam!
* module file tutorial: updated Dockerfile + minor changes in introduction
