New docs.openstack.org/index.html page

Sync with havana/index.html

This still points to /trunk instead of havana but it puts all books
already up there.

Change-Id: I0c57add2268c3051a5f0e59268f4553eececc165
Add a section about OpenStack distribution packages

Since many users are using distribution packages, let's give
some quick pointers to the distribution start pages.

Change-Id: I1843e278ac1757961092ee171ffc81aaf2da7426
Flattened chapter structure.

Added basic Manage Services chapter, and placed Identity and Compute sections inside. Redid Compute section header to match. Removed installation instructions (user should already have installed).

Change-Id: Iffb15804ea7c3b6e6ebed526fdd17c4e125184a8
Add "region" to glossary.

Change-Id: I8c66214088cc6c12f5fe16b962644dc9cae57aeb
Merge "Add "region" to glossary."