single child elements moved to parent level css pending

1) added attribute "hasOneChild"(default false) to Tent.Application.MenuItemView
2) added a check in function checkChildEntitlements: if no of entitled child views is 1 then set "hasOneChild" to true
3) added a check in menu_item handlebar :if hasOneChild is true then display the child view in the main menu itself.
 
pivotal story referance
https://www.pivotaltracker.com/story/show/61909546