New GUI in progress :

- main social account creation screen is completed ;
- facebook account creation screen is completed ;

* adapted faceboon account creation controller to new architecture and is now fully supported!

+ added new service : Social Account Service to manage social account creation.
+ added in this service a method to add a social account into the database whatever social account it is

+ added "final" (readonly) property to all variables that are not supposed to be modified. There were a lot of them !
Merge branch 'development' of github.com:Bessalel/MySocialFeed into development