Update to jni-rs v0.20 for android

[qdot]

Feature Description

Lots of new features came in, but this will require some reworking jni-utils-rs.

[atouchet]

jni 0.22 is out now.

[qdot]

Yup, I'm aware. This port is... extremely difficult at this point, since the change from 0.19 to 0.22 spans multiple API epochs at this point. So I'm saving it until I have time to concentrate on it. Good things is that, with the new embedded test system, I at least have a way to verify on real hardware.

[qdot]

#462