Debugging gltf export

        <description>A Maven project implementing imagej-elphel plugin</description>

        <dependencies>

			<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->

			<dependency>

			    <groupId>com.google.code.gson</groupId>

			    <artifactId>gson</artifactId>

			    <version>2.9.1</version>

			</dependency>

			<!-- https://mvnrepository.com/artifact/com.googlecode.json-simple/json-simple -->

			<dependency>

			    <groupId>com.googlecode.json-simple</groupId>

			    <artifactId>json-simple</artifactId>

			    <version>1.1</version>

			</dependency>

			<!--  ssh support - see https://www.baeldung.com/java-ssh-connection -->

			<!-- https://mvnrepository.com/artifact/org.apache.sshd/sshd-core -->

			<dependency>

	 * @param debug_level if > 0; print number of tiles to correlate

	 * @return flowXY vectors only for tiles to be updated or null if no tiles left

	 */

	double [][] recalculateFlowXY(

	static double [][] recalculateFlowXY(

			final double [][] flowXY, // will update

			final double [][] flowXY_prev, // previous flowXY (may be null for tiles)   

			final double [][] corr_vectorsXY,