Tutor

- [Bugfix] Fix `pip install tutor-openedx`.

- [Bugfix] Fix login from localhost.
- [Bugfix] Fix Android app image build.

- [Improvement] Improve assets building for development.
- [Improvement] Support CMS login when the CMS is not a subdomain of the LMS.

- [Feature] Upgrade from Hawthorn to Ironwood.

- [Feature] Multiple platforms on a single server \o/.
- [Feature] Easily configure web proxy on the host.
- [Bugfix] Fix `images pull all` command which failed on "all" image.
- [Improvement] Add configurable MongoDB, SMTP and RabbitMQ authentication.
- [Improvement] Harmonize MySQL username/password configuration parameters.
- [Feature] Configurable and pluggable data storage backends (114).

- [Feature] Enable grade downloads by default (143).
- [Improvement] Remove orphan containers on `local start`.