New endpoint strategies & start of murmur3 hashing support

From Issue #56. A small extension that I've been using recently.

Idea is to create QueryHint's with Murmur3 hashes in the key field and to provide them to TokenRingEndpointStrategy with Command.Execute

I've had to change key object in QueryHint to BigInteger. Not sure if this is an issue?

RoundRobin yields better query spreading on small numbers of nodes than Random.

Some of this needs to re-thought/improved. Probably need to either move or create an interface to the new Murmur3 hashing functions in ValueSerialization, preferably in QueryHint and I'm not sure whether you'd want to chnage ICqlCommand.