Report to server on a separate thread asynchronously

Move HTTP communication bits inside an AsyncTask. This way
the service won't block while its reporting data to the
server.

This is also necessary to comply with strict Android checks.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Include minSdkVersion in Manifest

This enables a series of policy checks that we now comply.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Release 1.20

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>