New files + Node systems

-Added Node system for users (aptly named struct node) and for Messages
(struct message)
-(Poor) initialization done in main
-Added some of the core functions (showItem, deleteItem, newItem)
-Added a topUsers array (will convert to pointer in a future commit,
it’s an array temporarily just to show that it’s going to be a
conjunction of Users)
-Added a topMsg (one list of messages per user)
Added temporary objects in gitignore