Remove cli functionality from bitcoind

As it says on the tin. It was deprecated in version 0.9, and
at some point it should be removed.

Removes the dependency of bitcoind on libbitcoin-cli.a. Move
some functions that used to be shared but are now only used in
bitcoin-cli.cpp to that file.

After this change, an error is printed (and exit code 1 is returned)
when the user tries to send RPC commands using bitcoind.

src/rpcclient.h

@@ -10,16 +10,6 @@
 #include "json/json_spirit_utils.h"
 #include "json/json_spirit_writer_template.h"
 
-int CommandLineRPC(int argc, char *argv[]);
-
 json_spirit::Array RPCConvertValues(const std::string &strMethod, const std::vector<std::string> &strParams);
 
-/** Show help message for bitcoin-cli.
- * The mainProgram argument is used to determine whether to show this message as main program
- * (and include some common options) or as sub-header of another help message.
- *
- * @note the argument can be removed once bitcoin-cli functionality is removed from bitcoind
- */
-std::string HelpMessageCli(bool mainProgram);
-
 #endif