revert deprecated block_type change for local_resource_url
Merge pull request #253 from aboudreault/revert-block-type-change-rebase

revert deprecated block_type change for local_resource_url
Add remove_user_from_cohort function in cohorts module

Conflicts:
	common/djangoapps/course_groups/cohorts.py
removed usages of missing CourseUserGroup.WORKGROUP