Fixes and improvements (#132)

- Fix glitch when turning on WiFi: It would temporarily show "No networks found" right before starting the first scan.
- Fix spinner to use Assets.h
- Replace statusbar battery icons 
- Better statusbar icon for when WiFi is on but not connected
- Replace statusbar WiFi icons and Wifi Manage RSSI/lock icons
- Fix for crash when timer is null in I2cScanner
- Deprecate Spacer
- Fixes for toolbar layout (simplified)
- Improved ImageViewer app: center image and add filename text on the bottom
- Add LV debug params to sdkconfig.developer
- Disabled LV spinner, msgbox and window widgets. These have equivalents in Tactility.

Tactility/Source/app/i2cscanner/I2cScanner.cpp

@@ -162,7 +162,10 @@ static void onHide(AppContext& app) {
 
     bool isRunning = false;
     if (data->mutex.acquire(250 / portTICK_PERIOD_MS) == TtStatusOk) {
-        isRunning = data->scanTimer->isRunning();
+        auto* timer = data->scanTimer.get();
+        if (timer != nullptr) {
+            isRunning = timer->isRunning();
+        }
         data->mutex.release();
     } else {
         return;