This should fix issues with segfaults when the server is being
terminated that sometimes occur because things like NPC path traversal
keep running while the process is executing the signal handler.
* Use a specialized connection object
* Copy the Player object less frequently
* Use a randomly generated serial key for shard auth
* Refuse invalid shard connection attempts
* Clean up connection metadata when a Player joins the shard
* Prune abandoned connections when they time out
CNProtocol, CNShared, CNStructs and Defines are now in core/.
CNLoginServer, CNShardServer and Monitor are now in servers/.
core/Core.hpp wraps all the core headers except for CNShared.hpp.
Defines.cpp has been renamed to Packets.cpp, and so has its
corresponding namespace, but not the header file. This is in preparation
for upcoming changes.
