Feat: in text UIs, show render progress in one line (#257)

The text UI gets quite messy during the render process, as it takes at least one extra line of the screen per second. This PR fixes that issue and also shows an ASCII bar to show the render progress.

src/com/sheepit/client/Gui.java

@@ -28,6 +28,8 @@ public interface Gui {
 	
 	public void status(String msg_, boolean overwriteSuspendedMsg);
 	
+	public void status(String msg_, int progress);
+	
 	public void status(String msg_, int progress, long size);
 	
 	public void updateTrayIcon(Integer percentage_);