Warn on unhandled Factorio ipc

Send warning to console if an ipc message is received but there were no
handlers registered to handle it.

lib/factorio/server.js

@@ -505,7 +505,9 @@ class FactorioServer extends events.EventEmitter {
 			throw new Error(`Unknown IPC type '${type}'`);
 		}
 
-		this.emit(`ipc-${channel}`, content);
+		if (!this.emit(`ipc-${channel}`, content)) {
+			console.warn(`Warning: Unhandled ipc-${channel}`, content);
+		}
 	}
 
 	_handleOutput(line, source) {