REST: Add base configuration hooks for a REST API

REST: Add base configuration hooks for a REST API

This adds the ability to expose a REST API based on the Django REST
framework project. Since this project isn't packaged in most current
distributions, we ensure that its both installed and enabled before
trying to use it.

Signed-off-by: Andy Doan <andy.doan@linaro.org>
Inspired-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Stephen Finucane <stephen.finucane@intel.com>