Adding in templates for rendering of Student Training Examples.
Merge branch 'authoring' of https://github.com/edx/edx-ora2 into grady/student-training-authoring-templates

Conflicts:
	openassessment/xblock/static/sass/oa/utilities/_developer.scss
Merge branch 'authoring' of https://github.com/edx/edx-ora2 into grady/student-training-authoring-templates

Conflicts:
	openassessment/xblock/static/css/openassessment.css
Merge branch 'authoring' of https://github.com/edx/edx-ora2 into grady/student-training-authoring-templates

Conflicts:
	openassessment/xblock/static/sass/oa/utilities/_developer.scss
Added in templates for Student Training Authoring
Included:
- HTML Templating using current problem defininition
- Styles
Not included:
- JavaScript changes
- Python test cleanup
Merge branch 'authoring' of https://github.com/edx/edx-ora2 into grady/student-training-authoring-templates

Conflicts:
	openassessment/xblock/studio_mixin.py
Merge pull request #502 from edx/grady/student-training-authoring-templates

Grady/student training authoring templates