[WIP] Logging on JNI level

In order to be able to debug on the JNI level, we can log to the ordinary Android log. In this PR, I have added logging of all calls to shared group method. This is work-in-progress - we should be able to log all calls in the other modules and log values of essential variables and parameters.

@bmunkholm @cmelchior @emanuelez 
I would initially skip all the LEAVE macros - they won't add much value unless you debug something specific, but they would be noisy. Another alternative is to disable LEAVE in general in the macro but "leave" the macros here. That's faster and more flexible.