Mostly just re-arranging guides in groups, but also updating more text.

Added new information about graphics on Ubuntu 14.04 EC2 instances,
also added a new guide highlighting some of the existing pvweb
applications, put this new guide into a new section called Sample
Applications.  Fixed up some of the Apache as a front end text as
well.

Change-Id: Id6e79c308d63414379779e4a9d5e3419de9ffb99
Merge topic 'pvweb-docs-further-reorganization' into next

720d7162 Mostly just re-arranging guides in groups, but also updating more text.