Proposed enhancements for Neuroglancer

1. Drawing tool that allows the user to draw continuous lines around a shape.
2. Annotation tool to add text to a layer.
3. Get a good set of COMs/brain in the alignment dropdown.
4. CVAT import of annotations - done
   1. Get DK52 CH3 aligned images into CVAT, sections 200 -> 220,
   2. Normalize them so just the starter cells show up and import into CVAT
   3. Import that section data annotations into CVAT.
   4. Export that CVAT annotation data, rescale then import into Neuroglancer.
   5. Look at the output in Neuroglancer.
5. Upgrade CVAT
6. Add link in Django that points to CVAT - done