Layout: Add `forgetLazyState` method

apps/weather/app.js

@@ -74,7 +74,7 @@ function update() {
   if (current) {
     draw();
   } else {
-    delete layout.rects;
+    layout.forgetLazyState();
     if (NRF.getSecurityStatus().connected) {
       E.showMessage("Weather unknown\n\nIs Gadgetbridge\nweather reporting\nset up on your\nphone?");
     } else {

modules/Layout.js

@@ -73,6 +73,7 @@ Other functions:
 * `layout.update()` - update positions of everything if contents have changed
 * `layout.debug(obj)` - draw outlines for objects on screen
 * `layout.clear(obj)` - clear the given object (you can also just specify `bgCol` to clear before each render)
+* `layout.forgetLazyState()` - if lazy rendering is enabled, makes the next call to `render()` perform a full re-render
 
 */
 
@@ -258,6 +259,10 @@ Layout.prototype.render = function (l) {
   }
 };
 
+Layout.prototype.forgetLazyState = function () {
+  this.rects = {};
+}
+
 Layout.prototype.layout = function (l) {
   // l = current layout element
   // exw,exh = extra width/height available