Profile privacy feature

https://www.pivotaltracker.com/s/projects/982890 
https://www.pivotaltracker.com/s/projects/982890/stories/64970358
https://www.pivotaltracker.com/s/projects/982890/stories/65424974

-  fix for back button (legacy URL issue plus bug open by Pavel)
-  per Thomas fixed the carot on sidebar from upward to right facing position.
-  added ul, li and target to html whitelist in documents_helper.rb 
-  added public/private profile feature
-  added controllers specs and cukes scenario to test private profile is hidden
-  implemented pending steps in users_controllers_spec.rb file