Factor out a lot of the information encoded into JSON-RPC functions into
a table storing metadata.  This simplifies implementation of the RPC
functions, and allows the CLI to do a better job of parsing arguments
and formatting results.

Conflicts:
	libraries/rpc/include/bts/rpc/rpc_server.hpp
	libraries/rpc/rpc_server.cpp
Compile fixes after merging in http rpc commits