Improve transparency for BW devices
Improve transparency for BW devices

With new SDK4 transparent PNGs now work for Aplite (and Diorite) when
using GCompOpSet, removed usage of GCompOpAssign for mono devices.

clach04/pebble_tz,clach04/watchface_framework,clach04/pebble_tz,clach04/watchface_framework,clach04/watchface_framework,clach04/pebble_tz