Initial commit: template pindah repository

Our previous attempts with PyJNIus/ Kivy was unsuccessful.  Maybe
mirah is the way forward?
Rakefile: target Android 4.2
ChwallActivity: call gallery-picker

Next, we have to figure out what to do with the result.
ChwallActivity, AndroidManifest: change wallpaper to const
ChwallActivity: onActivityResult() finally triggered
ChwallActivity: set wallpaper to chosen image
.gitignore: ignore Emacs temp files