Add a GameTimer class to provide reference timestamps during a game.
Add sending and receiving ping_packets.
Check protocol and version of received datagrams.
Add some logging.
Fix confusion between packet ID and packet type.
Log received packet ID.
Fix GameTimer namespace.
Use a #define for the verbose log level used when logging datagrams.
Minor typos.
Merge pull request #7 from Neki/topic/bf_client_network

Client-side networking.