Revisiting this again; the issue was that the comparison operator was
facing the wrong way, so connections were being pruned every 30 seconds
or less. This was effectively a race condition kicking an unlucky player
every so often when pruning happened exactly during an attempt to enter
the game.
Now that the proper timeout is being enforced, I've reduced it to 5
minutes, down from 15, since it really doesn't need to be that long.
* Separate pruning frequency from timeout
* Pluralize CNShared map: login -> logins
* Increase connection timeout to 15 minutes
* Do not deallocate a nullptr in playerEnter()
* Kill connections rejected by playerEnter()
* Remove redundant inclusions of mutex headers in a few places
* 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.
