Fix various oversights/bugs in ZMQ RPC server code

- Add some RPC commands (and touch up a couple others)
- some bounds checking
- some better pointer management
- const correctness and error handling

-- Thanks @vtnerd for type help with serialization and CMake changes

src/daemon/command_line_args.h

@@ -83,12 +83,6 @@ namespace daemon_args
       , std::to_string(config::testnet::ZMQ_RPC_DEFAULT_PORT)
   };
 
-  const command_line::arg_descriptor<bool> arg_zmq_restricted_rpc = {
-    "zmq-restricted-rpc"
-      , "Restrict ZMQ RPC to view only commands"
-      , false
-  };
-
 }  // namespace daemon_args
 
 #endif // DAEMON_COMMAND_LINE_ARGS_H