Print an error when second byte of "swap buffers" is not 0

As discussed in #42

CHANGELOG.md

@@ -80,7 +80,8 @@
 	* logfiles are now saved in a `logfiles/` subdirectory
 	* more helpful "disconnected" overlay in live mode (displays server IP and port)
 	* major improvements to the behavior of windows with multi-monitor setups (among other things, dialogs are now displayed relative the the main window as opposed to always being on the primiary monitor)
-	* added a way to select players with the drawing API
+	* added a select players command to the drawing API: `| 3 | 0 | Agent/Team |`
+	* the swap buffers command now prints an error when the second byte does not equal 0 instead of ignoring it, making the behavior consistent with the rest of the drawing API
 	* added a black outline for the player numbers texts
 	* moved `config.txt` out of `resources/` into the root directory for easier access
 	* moved build scripts to the `scripts/` subdirectory

src/rv/comm/drawing/commands/DrawOption.java

@@ -35,9 +35,16 @@ public class DrawOption extends Command {
     public DrawOption(ByteBuffer buf, Viewer viewer) {
         this.drawings = viewer.getDrawings();
 
-        // currently only one type of draw option (swap buffers)
         int type = ByteUtil.uValue(buf.get());
-        setName = getString(buf);
+
+        switch (type) {
+        case SWAP_BUFFERS:
+            setName = getString(buf);
+            break;
+        default:
+            System.err.println("Unknown draw option : " + type);
+            setName = null;
+        }
     }
 
     @Override