add-cluster: reduce montage to managable size
add-cluster: reduce montage to managable size

The resulting montages can be pretty huge, reduce them such that their
maximum height or width is 1024. This will save a lot of space and
shouldn't throw away any useful information - the really detailed
images will come from the USB microscope.

Test Plan:
Try to add a new cluster with the 'mel add-cluster', fail with
NotImplementedError as expected.

aevri/mel,aevri/mel