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 

Can you merge master into this branch?  I made a fix for this already -- one of the instances should have been `FILE_ADD_TO_WORKINGSET` and this will effectively remove it I believe.