removed blocking calls

[molbertz]

These are the changes which now only have non blocking calls. But maybe we should re-add the blocking ones as deprecated to not break the API.

[jperedadnr]

Great, looks good. Just realised there is one final thing left to do: can you please update also the sample snippet in the javadoc?

Something like:

 * <pre>
 * {@code BarcodeScanService.create().ifPresent(service -> {
 *      service.resultProperty().addListener((obs, ov, nv) ->
 *          System.out.printf("Scanned result: %s", nv.getResult()));
 *      barcodeScanService.asyncScan();
 *  });}</pre>

[molbertz]

Oh yes, that makes sense. Do you want to replace the deprecated example or keep it?

[jperedadnr]

No, just remove it