Integrate Image Sequencer changes to accept any processing string format

[jywarren]

After this is complete: publiclab/image-sequencer#731

we should be able to pass in any string format, including multiple commands, like brightness,ndvi,colormap or brightness{brightness:80}, or object format commands, as in the Image Sequencer docs. https://github.com/publiclab/image-sequencer/

This should begin working as soon as the above issue is solved - we can just pull in the new version of IS.

[jywarren]

Now waiting on a bugfix via publiclab/image-sequencer#1030... should be soon!