MySQLDataProvider Connection Pooling

Added connection pooling to the MySQLDataProvider, allowing multiple threads to access the database concurrently.

As threads attempt to access the database concurrently, connections will be formed as needed, up to a configurable maximum.

All logging requests are now handled asynchronously, alleviating an issue where the server would stall waiting for large amounts of logging to complete.
WorldContainer Automatic Client Removal

The WorldContainer object will now automatically remove disconnecting clients, eliminating any risk of disconnected clients remaining associated with columns (thereby keeping them loaded).
Seed

Added a method to the WorldContainer class which retrieves the seed.

Essential for implementing generators/populators.
Cleanup

Removed unused/unnecessary/outdated file world_gen.hpp.
Packet Update

Fixed the definitions for packets 0x13 ("Entity Action") and 0xCA ("Player Abilities").