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 
Small style suggestions on these tests:

1) Since in the "happy path" case event listeners will be installed, I'd prefer for `addEventListeners()` to be called in `beforeEach()`

2) I'm not sure that "does not add an element when there are not event listeners" accurately represents the bug.  If you wanted to more closely replicate the issue, you could instantiate multiple containers, click the add button, then verify that the number of items increases by 1.