lib/jvm: JavaObject is a Java Object (not a JNI jobject)

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
ffi/java: support inner classes and JNI format in extern Java types

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
Merge: Java FFI: support inner classes and use of JavaObject across the FFI

Minor incremental improvements to the Java FFI

Pull-Request: #463
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>