Completely changes Python installation

Removes libpython2.7.so we used until now
(c.f. github.com/NickStephens/python-sensor-extension)
due to lack of dependencies (e.g. libffi)
Adds python built by using kivy/python-for-android

This is what I did to get my python build
 - built a kivy sample app using:
 p4a apk --arch=armeabi-v7a --private=/home/lukas/kivy-app --package=org.example.myapp --name "My app" --version 0.1 --requirements=python2,libffi --sdk_dir=$HOME/Android/Sdk --ndk_dir=$HOME/android-ndk-r12b --android_api=21 --ndk_ver=r12b
 - deployed the app on a device to see if python install works
 - adb'ed into device
   - copied over lib/libffi.so and lib/libpython2.7.so to my repo
   - copied over files/lib/python2.7 files/lib/python27.zip to my repo
 - copied ~/.local/share/python-for-android/dists/unnamed_dist_n/python-install/include/ (python headers) to my repo

Above approach is just to see if we can use kivy python build for our native app
Later we'll base our python build and install on what kivy is doing!!