nitg/android: load assets on the APK

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitg/android: move generate apk file (with -o or locally)

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
example: update mnit examples with android version

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
NOTICE: updated with info of the libpng project

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>