check if variables are defined using proper ansible syntax

Feanil/abbey volume size

Feanil/import xml courses

Jenkins should save the state of the rbenv

Update mysql-python to 1.2.5 for jenkins_worker

Require versions for the course repo checkouts so we can match the versions in
production.

Update import script to spit out yaml configuration and XML mappings for mixed
module store.

Jarv/santize split

creating separate options to clean the prod_grader and wwc dbs

Needed for edge which doesn't have a prod_grader db

optionally override cms hostname in nginx

adding an option to override the default cache path for ec2.py

Han/fix motd

Correcting /usr/share/landscape file