[RDY] MsgPack-RPC dispatch based on function array lookup

This simplifies the generated msgpack_rpc_dispatch() function, separates the
code for each RPC method more clearly and allows easy implementation of
alternative dispatching methods (e.g. string method id dispatch).

This is how the generated code looks like: (UPDATED) http://pastie.org/9323657 (dropped some functions as this file exceeds pastie's size limit).