lua scripting support for JedisCluster

We added support for lua scripting to JedisCluster.

1. For script commands without keys like SCRIPT LOAD, an exception is thrown.
2. For multi-key script commands, all the keys should hash to the same slot otherwise and exception is thrown.
3. Added JedisClusterScriptingCommands that takes a key parameter for scriptExists and scriptLoad to select a specific node in the cluster.