Fix other app's graphics showing on image clock (BANGLEJS 1)

There is an issue, where if you open an app that has graphics on the bottom, and hold down BTN3 to go to the image clock, a small amount of the apps graphics (about 10px) will show on the bottom. This update just adds an initial clear, which clears other app's graphics.

I am using a banglejs v1 (firmware 2v21).

apps/imgclock/app.js

@@ -3,6 +3,7 @@ Draws a fullscreen image from flash memory
 Saves a small image to flash which is just the area where the clock is
 Keeps an offscreen buffer and draws the time to that
 */
+g.clear(); //clears other apps's graphics
 var is12Hour = (require("Storage").readJSON("setting.json",1)||{})["12hour"];
 var inf = require("Storage").readJSON("imgclock.face.json");
 var img = require("Storage").read("imgclock.face.img");