Define Firebase data structure to be used

[leynadm]

• 'user' collection should contain:(User ID), Name, Surname, Birthdate, Sex (Top Level Collection)
• 'posts':(Auto-generated post ID), User ID, Post Date, User Text, image url
• Followers-feed:(ID of the user being followed), 'lastPost' referencing last post made, users array field [containing all the users following the user], recentPosts array containing the Ids of the posts made by the user