Check that all po/pot files are valid

Perform minimal checks on po and pot files so that no broken files can
get imported.

Change-Id: Ic39d68106259a225fa5e5399123063e7c35ba150
Co-Authored-By: Clark Boylan <clark.boylan@gmail.com>
Related-Bug: #1299349
Restructured and updated basic environment config chapter

As part of the installation guide improvement project, I performed
the following operations on the basic environment configuration
chapter of the installation guide:

1) Split large ch_basics.xml file into smaller files to ease addition
   of new networking content and future updates.
2) Added information on how to install on VMs.
3) Added recommended minimum hardware requirements for each node.
4) Built detailed instructions for network configuration on
   three-node neutron and two-node nova example architectures
   including verification of connectivity using name resolution.
5) Clarified phrasing and wording.
6) Updated glossary as necessary.

This patch primarily updates networking content in this chapter.

Change-Id: Ib31a99448757d36ae29ff8069ddbeab8fe0106bd
Partial-Bug: #1291071
Implements: blueprint networking-install-guide-improvements
Fix example user-list in keystone install

In Icehouse, the response changed slightly, and we now add
a second user in the guide.

Change-Id: I38a72c9826ad6344db7ae11dce64b847e94bd746
Merge "Fix example user-list in keystone install"
Merge "Check that all po/pot files are valid"