Add HSTS and cookie security to dashboard example config

Adds reccomended settings from
https://bugs.launchpad.net/ossn/+bug/1191050
https://bugs.launchpad.net/ossn/+bug/1191051
http://docs.openstack.org/developer/horizon/topics/deployment.html#secure-site-recommendations
to the configuration instructions for HTTPS

Also includes some gramatical and formating fixes

Affects install guides, compute admin guide, and configuration guide

Note the content is in two nearly identical locations
https://bugs.launchpad.net/openstack-manuals/+bug/1222006
has been opened for the organizational bug.
This fixes the content of both locations identically.

Change-Id: I1b41b3bee0d884ca3d29a1f2667e5b55070131cb
Closes-Bug: #1210409
Merge "Add HSTS and cookie security to dashboard example config"