Dynamic configuration capability for Hbase.

I think, some preperties can be dynamically configured without restart of the nodes.
This is an umberilla JIRA for this Feature.

In Hadoop we already had such feature but not yet implemented by nodes. I think we can have the similar base framework here and can implemented by nodes. So, that whatever properies are allowed to reconfigurable, should be able to reconfigure with new values with out restarting the node.

I will come up with some design doc with noeds implementation and will raise subtasks for each.