devstack.org site updates

Includes:
* Change Precise to Trusty
* Add the new plugin phase
* Remove deprecated config options
* much, much more

Change-Id: I0385f18a3256ad37a611e505e49572f27b3bcc10
Merge "devstack.org site updates"
Merge commit 'refs/changes/83/86083/2' of git://gold.eng.hq.xensource.com/git/github/openstack-dev/devstack into tmpbranch