CYB-160 - Make Engagement Index work again + big refactoring

https://jira.ets.berkeley.edu/jira/browse/CYB-160


Changes to engagement index & point configuration

* Accessibility changes
* Make the code more DRY
* Split things up into templates
* Make the design between point configuration and engagement index more alike
* Use local image files instead of remote ones
* Make the image (screenshot) responsive
* Add util service for scrolling to an element
* Use the new `has_answered_share_question` value from the back-end
* Create overall CSS style classes and defaults
* Remove `enabled-javascript` reference since the tools will only be loaded within Canvas (requires JS)
@coyote @NolanChan Previously it was actually giving me the wrong user for `engagement_index_json["current_canvas_user"]` - please have a look at the other places in the code. Whether we should use `session[:canvas]['user_id']` or `session[:canvas_user_id]`.

Also created https://jira.ets.berkeley.edu/jira/browse/CYB-161 and assigned it to @coyote to follow up.