Support birth cohort. Feature #3461

There are several changes going on here most notably:

* Constants are created for the new birth cohort and pbs eligibility names.
* The creation of the event associated with a Contact is moved to the Contact object based on what kind of event it is
* ContactInitiateVC no longer sends out NSNotifications when it is done but instead uses the delegation pattern with RootViewController being the delegate object in this case.
* ContactinitiateVC is now nested in a UINavigationController in order to allow for smooth sliding between the new *ScreenerTypeChooserViewController*.
* ContactInitiateVC is now fully responsible for the handling of creation, reading, updating and deletion of a contact as opposed to RootViewController. (It was only responsible for reading, updating and deletion before…)
* EventTemplate now checks the database for the new name first and, if there is none, the legacy name second. 
* Wrote a test for checking to make sure that contactInititateVC is showing the event that was chosen by the ScreenerTypeChooserViewController.