OPS-1593 As an operator, I want sudo_user converted to become user in roles and plays, for compatibility with Ansible 2.x

In addition to validating our supervisor and nginx configurations, this ensures we can serve static files locally as we would in production.

The headers were pointing to the old github wiki. Since we've officially
moved to Confluence, these links should be updated.

This adds some helper scripts for managing the edx server.

In order to support --check we need to ensure that registered
vars exist before checking their stdout. Otherwise ansible
errors out.

Make it easier to use a local pypi mirror in the roles listed above

Always write the supervisor files and link them as necessary.

Drop the configs in the supervisor available directory. Instead of having a
seperate cfg dir for each service.

Seperate devstack logic from disabling supervisor tasks. Add the new flag so
devstack continues to not startup supervisor. Use new supervisor_available_dir
everywhere.

Remove mongo logic from abbey and remove stage_release. This should completely
remove our tie ins to mongo.

Also removing monitor repos script which depended on stage_release. We can add
in similar logic when we're ready to automate building the AMIs on rc branch
creation.

Updated requirements.

services if it changes
deploy tasks no longer stop the service and will notify the restart
if any task changes

This is so that we can have multiple supervisors running
in different virtual envs

prefix

Sets up a pypy mirror caching server