LPS-42322 - On mobile devices, child page dropdowns cannot be collapsed

Hey @natecavanaugh,

Attached is an update for http://issues.liferay.com/browse/LPS-42322.

NOTE: "QA failed the first fix for this ticket because they wanted the clickoutside behavior to be applied to the navigation dropdowns as opposed to it just being a toggle. You'll notice that the logic added in this commit looks pretty similar to that in menu_toggle.js, but with a few major differences that would make implementing the menuToggle component a pain. Doing it this way will be less destructive, with less chances of regression bugs. Let me know if you have any questions." - @Robert-Frampton 

Please let me know if you have any questions.  Thanks!