Custom content using tinymce (then convert to markdown).
Use tinymce for course handouts edit.
settings for Labster

- add `LABSTER` to `FEATURES`
- add `labster` to `INSTALLED_APPS`
- add `labster` to `urls.py`
- add `labster` repository to requirements
- use labster's django-wiki fork
"hack" to fix None pk_set in m2m_changed signals
Implement lab unit, a custom unit for labster
Implement lab unit, a custom unit for labster
Edit TOS page to be same with Labster TOS page
all students progress functionality is added
Merge remote-tracking branch 'labster/progress_all_students' into labster
Merge remote-tracking branch 'labster/labster' into labster
Merge branch 'tinymce-wiki'
Merge branch 'tinymce-course-handouts'
Merge remote-tracking branch 'edx/release'
Student quiz detail part 1
Delete temporary save file
Update student quiz detail
Add score in student quiz detail
Add link to student quiz detail
Merge branch 'labster-xblock' of https://github.com/Bodekaer/Labster.EdX into labster-xblock

Conflicts:
	lms/djangoapps/courseware/views.py
	lms/envs/common.py