Add support for incremental list updates

[englehardt]

Dimi has confirmed that we have support for this in the platform. Apparently we may also have server-side support [0]. If that works, maybe we just need to update the shavar-list-creation script to generate new “add chunk”(trackers to add) and “sub chunk”(trackers to remove) accordingly.

This would allow us to quickly review and merge list updates, rather than worrying about batching them due to cost.

[0] https://github.com/mozilla-services/shavar/blob/master/shavar/lists.py#L188

[groovecoder]

Another great idea ... may be some significant work and more meticulous release engineering to get this right.

E.g., we would have to tag versions in shavar-prod-lists when we release new list contents, and then we could use the version differences to generate the add & subtract chunks.

Will need some planning and design for sure.