XBlock Discussion changes

Conflicts:
	cms/djangoapps/contentstore/views/helpers.py
	common/static/coffee/src/discussion/content.coffee
	common/static/coffee/src/discussion/discussion_filter.coffee
	common/static/coffee/src/discussion/discussion_module_view.coffee
	common/static/coffee/src/discussion/discussion_router.coffee
	common/static/coffee/src/discussion/views/discussion_content_view.coffee
	common/static/coffee/src/discussion/views/discussion_thread_profile_view.coffee
	common/static/coffee/src/discussion/views/discussion_thread_show_view.coffee
	common/static/coffee/src/discussion/views/discussion_thread_view.coffee
	common/static/coffee/src/discussion/views/new_post_view.coffee
	common/static/coffee/src/discussion/views/response_comment_show_view.coffee
	common/static/coffee/src/discussion/views/thread_response_show_view.coffee
	common/static/coffee/src/discussion/views/thread_response_view.coffee
	lms/djangoapps/django_comment_client/forum/views.py
	lms/static/sass/discussion/_discussion.scss
	lms/templates/discussion/_discussion_module.html
	lms/templates/discussion/_filter_dropdown.html
	lms/templates/discussion/_js_head_dependencies.html
	lms/templates/discussion/_thread_list_template.html
	lms/templates/discussion/_underscore_templates.html
	lms/templates/discussion/index.html
	lms/templates/discussion/mustache/_inline_discussion.mustache
	lms/templates/discussion/mustache/_pagination.mustache
	lms/templates/discussion/mustache/_profile_thread.mustache
Add ENABLE_DISCUSSION_EMAIL_DIGEST in api_manager

Conflicts:
	lms/djangoapps/api_manager/users/tests.py