C++ server code

Latest master merged in. We should discuss the layout of the code.
The connection logic is handled by the server. event_handler is only executed if the server actually got some data from a client. The important if-statement is the ev == MG_REQUEST one. That's where handle_uri is called. MG_REQUEST means that the server identified a request of some sort from the client (POST, GET, etc.).

The server itself keeps going if there isn't a connection. It just keeps listening until one is established.