Column Loading/Sending Exception Safety

An exception while adding a player to a column/sending a column to a player will now cause the server to panic.
Random Number Generator Factories

The World class now has factory methods which allow random number generators of any variety (Mersenne Twister 19937 32-bit is default) to be created and deterministically (none of the methods used are platform dependent/implementation defined) seeded based on the world's seed and optionally a specific column.