Implement export of item icons and locale

Add mod and command for exporting the Factorio locale including mods,
and item icons assemled into a sprite sheet including mods.

lib/factorio/server.js

@@ -955,6 +955,18 @@ class FactorioServer extends events.EventEmitter {
 		}
 	}
 
+	/**
+	 * Kill the server
+	 *
+	 * Terminates the server without any cleanup or saving.
+	 */
+	async kill() {
+		this._check(["running", "stopping"]);
+		this._state = "stopping";
+		this._server.kill("SIGKILL");
+		await events.once(this._server, "exit");
+	}
+
 	/**
 	 * Disable achievements on the running server
 	 *