theming support + playbooks/edx-west symlinks + redo edxapp deploy

This commit basically does 3 things:
* Creates symlinks within the playbooks/edx-west directory
  to allow ansible-playbook to be run in that directory
* Adds support for creating theming directory and checking out
  themed git repo into that directory at deploy time.
* Moves around some of the edxapp deploy handlers.
  Also tags them all with - deploy, so that running
  ansible-playbook with --tags=deploy basically just deploys.
  Also splits restart edxapp into stop and start edxapp b/c
  restart wasn't working on Stanford servers.  Could debug
  this later, probably best by looking at the edxapp upstart script.