Have the Dog detector accept 1D images.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Make the Downsample detector accept 1D images.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Slightly less stupid default values for blob diameter.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>