Update JNI bindings

The LibVCFNative bindings are produced with javah.

To build the binding you must first compile the java file to a class file:

cd api/spark/src/main/java/io/tiledb/libvcfnative
javac LibVCFNative.java

Next you can use javah to rebuild the LibVCFNative header:

# Navigate back to top level spark src directory
cd ../../../
javah -v -cp $PWD -o io/tiledb/libvcfnative/LibVCFNative.h io.tiledb.libvcfnative.LibVCFNative

It is safe to delete the class file now:

rm io/tiledb/libvcfnative/LibVCFNative.class