consolidating lms/cms/lms-preview into edxapp role

Creates edxapp upstart job and combines lms, lms-preview. cms
into the edxapp role.
adding comment to explain json vars
updating example playbooks
mainly fix gunicorn templates for var format consistency
add toggle variables to lms/cms/preview/xml
Merge pull request #86 from edx/jarv/edxapp

consolidating lms/cms/lms-preview into edxapp role