Exploring integration of django-modeltranslation.

A note to the Torchbox folks. To give changes here a look you will want to also see changes on master at https://github.com/p97-labs/wagtaildemo.

The primary hurdle seen in integrating Modeltranslation with Wagtail as I went about it was saving (drafts and publishing).

Some references I used:
https://django-modeltranslation.readthedocs.org/en/latest/
https://docs.djangoproject.com/en/dev/topics/i18n/translation/