[#2289377] Add profile/login links back to main navigation
[Fixes #66120056 IsEmpty
[Fixes #66120128] LinkedList_Size
Add size method
Add AddToFront method [#66120608]
Add AddToFront method [https://www.pivotaltracker.com/story/show/66120608]
Add AddToBack method [#66120708]
Add ValueAtIndex method [#66120680]
Add ValueAtIndex method [#66120914]
Add ValueAtIndex method [#66279606]
Add ValueAtIndex method [#66279606]
Add various [#66279606]