Consolidate FindJNI

[Chris Hillery]

We have FindJNI.cmake in Zorba itself, in the util-jvm module, and in (at least) the schema-tools and data-formatting modules. They're probably somewhat different, and whenever we need to make changes we need to change them all individually.

My preference would be to consolidate all of this into the util-jvm module, and provide a way (possibly via UtilJavaUse.cmake) for all other modules to find JNI using the version shipped with util-jvm.

I'm not sure how to handle the FindJNI.cmake that is in Zorba itself - it apparently is used for the Java language binding, and this should not depend on the util-jvm module. But, we can't make all modules use the version inside Zorba unless we add FindJNI.cmake to the list of installable files from Zorba, which seems a little weird too.