adding link clicked event and associated tests

common/test/acceptance/tests/lms/test_lms_courseware.py

lms/envs/common.py

lms/static/js/bookmarks/bookmarks_factory.js

lms/static/js/courseware/courseware_factory.js

lms/static/js/fixtures/courseware/link_clicked_events.html

lms/static/js/spec/courseware/bookmark_button_view_spec.js

lms/static/js/spec/courseware/bookmarks_list_view_spec.js

lms/static/js/spec/courseware/course_home_events_spec.js

lms/static/js/spec/courseware/link_clicked_events_spec.js

lms/static/js/spec/courseware/updates_visibility_spec.js

lms/static/js/spec/main.js

lms/static/lms/js/build.js

lms/templates/courseware/courseware.html