Implement `toBounds()` collector

[jenetics]

For some GPX files, the Bounds metadata is missing. Add a collector, which allows to collect the boundaries of a given WayPoint stream.

static Collector<WayPoint, ?, Bounds> toBounds();

final Bounds bounds = gpx.tracks()
    .flatMap(Track::segments)
    .flatMap(TrackSegment::points)
    .collect(toBounds());

[jenetics]

static Collector<WayPoint, ?, Bounds> toBounds() {
    return Collector.of(
        () -> {
            final double[] a = new double[4];
            a[0] = Double.MAX_VALUE;
            a[1] = Double.MAX_VALUE;
            a[2] = Double.MIN_VALUE;
            a[3] = Double.MIN_VALUE;
            return a;
        },
        (a, b) -> {
            a[0] = min(b.getLatitude().doubleValue(), a[0]);
            a[1] = min(b.getLongitude().doubleValue(), a[1]);
            a[2] = max(b.getLatitude().doubleValue(), a[2]);
            a[3] = max(b.getLongitude().doubleValue(), a[3]);
        },
        (a, b) -> {
            a[0] = min(a[0], b[0]);
            a[1] = min(a[1], b[1]);
            a[2] = max(a[2], b[2]);
            a[3] = max(a[3], b[3]);
            return a;
        },
        a -> Bounds.of(a[0], a[1], a[2], a[3])
    );
}

[jenetics]

Merged into r1.6.0 branch.