Making event listener registering explicit for containers

This is a fix for https://openedx.atlassian.net/browse/ORA-709
Where in multiple options are added when you click an add button once. This is due to too many event listeners being registered on a single DOM element. 

This PR makes adding event handlers an explicit event when constructing the initial containers. This means other requests to navigate the containers will not trigger re-creation of event listeners. 

Tests updated. An additional test created for checking that event listeners are not registered when not explicitly created.

@wedaly @gradyward 
Done; the one addEventListeners() you commented on would stay in, though, since the container is created within the test with a new element.