Update NodeStats length types

NodeStats int lengths were not proper for the data types returned here,
longs should be used instead.
Add support for /_cluster/state

Add initial monitoring support via /_cluster/state, incomplete on
metadata and blocks but the majority of the objects are present/mapped.
Add missing ClusterStateInfo.cs
Merge pull request #292 from NickCraver/master

Support for /_cluster/state APIs