Simplify usage of nodes info API

Important: This breaks backwards compatibility with 0.90

* Removed endpoints: /_cluster/nodes, /_cluster/nodes/nodeId1,nodeId2
* Disallow usage of parameters, but make them required part of URI instead
* Changed NodesInfoRequest to return everything by default
* Fixed NPE in NodesInfoResponse

Closes #4055

**Note**: Before this should is going to be pushed, #4057 must be changed as well, because some URLs overlap and are not returned correctly