edxapp-perm-fixes: Make sure virtualenv exists before using python
edxapp-perm-fixes: Create directory for staticfiles with edxapp user
edxapp-perm-fixes: Stopped edxapp services only need to be started, not restarted
edxapp-perm-fixes: Ensure all edxapp venv files are readable by any user

For pip packages which create group-restricted venv files (httplib2).
edxapp-perm-fixes: Ensure edxapp/edxapp_worker are available in supervisor

Right after they are added for the first time, the commands are not available
until the groups are added.
Merge pull request #405 from antoviaque/edxapp-perm-fixes

Fixes for edxapp: Permissions & supervisor startup/configuration