Implement Split View Menus

Split View Menus:

* Remove temporary menu items
* Add Split view icon w/tooltip
* Change Split view icon state based on split view scheme
* Create permanent menu
* Localize menu strings
* Fix gear menu so it's always at top of sidebar, add tooltip

cc @JeffryBooher 

That's true for CSS but I'm talking about navigating the DOM so that `$sidebar.find("#working-set-spliview-btn")` is guaranteed to be attached to a single element. Doing so means that the menu handling code can move out of `SideBarView.js` and back into `DefaultMenus.js` where it was before I started work on SplitView. I needed to move it out because you can't attach an event listener to a node that doesn't exist. `$(".working-set-gear-menu").on("click", function() {});` wouldn't work. because the DOM nodes were being created when `WorkingSetView` objects are rendered.  Now that you've moved the DOM elements back into `main-view.html`, we can attach the event listeners to those DOM elements as soon HTML Ready which is what we do for other default menus.