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: I24e8543006830d0b0b1781bc2746b8eac700a971
Co-Authored-By: Clark Boylan <clark.boylan@gmail.com>
Related-Bug: #1299349
Fix up installation guide

 + added a new page dedicated to Sahara configuration

Partial-Implements: blueprint update-docs-icehouse
Change-Id: If9a65ab165e1ecf52f0e71d7f1dbedeea1661470
Merge "Fix up installation guide"
Merge "Check that all po/pot files are valid"