Remove issue queries for 7dav data

[brookslogan]

Eventually queries for 7dav issue (but not as_of) data will be going away, and we'll want to use slides / caching derived archives to calculate them anyway. We should change all (archive) data objects, examples, vignettes, etc. to avoid these queries. Also check epipredict.

[brookslogan]

Performing this calculation intelligently (without repeatedly recalculating 7dav's that haven't changed) will require some of the same logic as developed in server-side JIT. We would also want to compactify along the way as in #173.

[brookslogan]

JIT isn't happening soon; we want this instead to give correct results on some signals with bad 7dav data, or just for the functionality.

[brookslogan]

We probably don't need this for any of the current vignettes.

[dshemetov]

Closing as outdated.

[brookslogan]

This is still sort of relevant due to potentially-buggy vignette data cmu-delphi/epidatasets#9, but I think we have the required archive -> archive transforms probably in some other issues.