Fix the various memory leaks that prevent Open MCT from being unloaded from the browser

[akhenry]

Summary

A lot of Open MCT code assumes that the application is never unloaded from the browser. This is true in normal usage, but our test specs rely on being able to cleanly load and unload Open MCT.

Expected vs Current Behavior

• All event listeners must be removed on application destroy.
• All stateful libraries (I'm looking at you AngularJS) must be cleanly unloaded when an Open MCT instance is destroyed.

Impact Check List

• [ ] Data loss or misrepresented data?
• [ ] Regression? Did this used to work or has it always been broken?
• [ ] Is there a workaround available?
• [ ] Does this impact a critical component?
• [ ] Is this just a visual bug?

[akhenry]

Testing notes:

• Verify that tests run correctly
• There are no functional changes here, so there is nothing specific in the application to test, however it is possible that bugs were introduced. The JavaScript console should be observed for errors during normal usage of the application.