Updated mongo role to be more flexible for different deployment scenarios

Added host parameter in the testing process of forum role

making lms/preview/cms ports env vars

Ensure the xqueue user and home directories exist.

Jarv/edxapp mixedmodule

Consolidate requirements.txt into a single file.

Stop referencing non-existent vars file.

Feanil/flatten vars

edx-west prod: don't install notifiers yet

The notifier isn't ready yet, needs theming to be done before it can be
installed.

edx-west: toggle carnegie institute to prod

Notifier config improvements: db dir, email vars

Added task to make sure elasticsearch is started

Allow configuration of IP Address of app servers to listen on

Modified vagrant-fullstack by using sandbox role definitions - Tested

rabbitmq-atp-update: Fixes "Failed to find required executable rabbitmq-plugins"

Forum role port test now properly uses host argument

- specify notifier_db_dir as a setting.  Had previously just stuck
  under $HOME, but Jim preferred as a distinct setting.

- pass through email settings env variables

- plumb through django's EMAIL_USE_TLS setting.  Required to be
  able to send mail using Amazon SES.  They speak smtp, but only
  over TLS.

E0d/fix github users

Notifier install fixes / seen while installing at Stanford