minor visual improvements, color adjustments
fix crash on new game from finish activity, when client == null

TODO: find out, why client might be null in onActivityResult
remove development warning on app start after upgrade
AndroidManifest: request com.android.vending.BILLING permission to prepare for in-app donations
renderer: prepare path for software renderer

don't call glGetFloatv on software renderer, because it's not implemented
view: generalize shadow methods for effects
view: add dropshadow to undo effect
intro: render stone dropshadow