Namespaced crypt package #2

This PR adds namespaces to all the Crypt\* classes and implements PSR-4 autoloading.

Squashed version.
Agreed, but to be fair, I think that whole switch block is unintuitive. There is no reason for the class_exists check in the first place, because it would always exist, unless the file was deleted. For almost every circumstance, this block will always use AES as the crypto, since that class will usually always be present. There needs to be a better mechanism to tell Random which crypto algorithm to use that doesn't require files to be deleted.