Added RpcResultBuilder class

Added a DSL-like builder class for creating RpcResult instances. This class will
deprecate the static Rpcs and RpcErrors classes in the controller.

Also added more javadocs to the RpcResult and RpcError interfaces.

Change-Id: I30cffc68419ed493035ba5fef466096bcec9df70
Signed-off-by: tpantelis <tpanteli@brocade.com>
Merge "Added RpcResultBuilder class"