Set up User Guide

This guide has been ordered to have sections that parallel
  what is in the introductory table, with screen shots, instructions,
  and appropriate xrefs in the same order as the table

Moved info about mapping logical-to-physical NICS from pre-install
Moved info about configuring the PXE network before deploying environment
  from install-guide
Added information about booting node servers before deploying environment
Deleted some superfluous and illegible screen shots that are now replaced
  by material in user-guide
Added "Configure Hardware" from information that was in the pre-install
  "Prerequisites" table.

TODO(Meg McRoberts):
  - Modularize the sections about each task/screen into separate
    files
  - Rewrite the intro (as well as the intros for Pre-Install and Install
  - A couple of screen shots are missing
  - Add xrefs to sections in other docs for supporting information.

Closes-Bug: 1289668
Closes-Bug: 1308279

Change-Id: Ie717a0fafbf40272f603bab361046fa36457501a