Remove the restart handlers for lms cms and lms-preview.

These handlers aren't being used by anyone and have been superceded by
the handler that starts and stops all edxapp components.
Remove empty gunicorn vars file.
Use Jinja templating syntax.
Move gunicorn install to common.
Use Jinja syntax.
Move loading edxapp upstart script to edxapp role.
Look for the upstart templates locally only.
Move edxapp upstart tasks into edxapp role.
Remove gunicorn role.
Merge pull request #112 from edx/feanil/edxapp_gunicorn

Feanil/edxapp gunicorn