Chaquopy: Python 2 for Android

Mar 16, 2018

Demo app:
* Remove READ_LOGS permission: this was only needed on API level 15, and its Google Play description is too scary.

SDK:
* The import hook now only looks up names in Java if they failed to import from Python.
* General performance improvements: the Python unit tests now run about 25% faster.
* Fix a crash on API level 15 caused by the license notification.