Change Add Menu Item button to same style as other pages

The other day I submitted a patch that restored the missing "Add Menu Item" button to the menus page, however I placed it at the bottom of the page.  I just discovered that other pages place such functions in the "notched" dropdown menu in the upper right corner.  This patch moves the button to that menu for consistency.

I have restricted the "Add Menu Type" and "Remove Menu Type" operations to administrators only.  Hopefully that is how you want it to work.