Bug 895569 - Remove django-bootstrap-forms and cleanup

* Remove django-bootstrap-form package
* Implement what we needed from it in mozillians
* Move some label text to form definitions
* Mark labels on required fields automatically with 'required' class
* Use CSS to visually differentiate required fields where desired
* Get rid of Jinja macros in edit_profile.html
* Try to move decisions about markup from Python to the template