This PR supports cropping vector images and does some small clean up / expansion of support for the "channels_first" property of vector images which is relevant for converting to numpy.
coverage: 84.688% (-0.008%) from 84.696%
when pulling d631b01baa554ed9491d0aeb650d9d37f6a4ccb1 on crop-vector-images
into 342603f9674402dcfb0b872905dcfd4099d32977 on master.
This PR supports cropping vector images and does some small clean up / expansion of support for the "channels_first" property of vector images which is relevant for converting to numpy.