Support uploading Shapefiles as a single .zip

[trevorgerhardt]

Users often have Shapefiles in packaged in a zip. If we additionally allow them to upload the zip, that would save them from needing to unzip and multi-select the individual files.

Additionally, we have had a user report that their IT network blocks some of the sidecar files from being uploaded and therefore they are unable to create opportunity datasets.

We should prioritize supporting this there, but also be consistent across the application.

An alternative solution is to add support for GeoJSON (which is desirable anyway), then convert their Shapefile in the browser before uploading.

[abyrd]

If possible we'll want to support ZIP on all uploads, because we support single-file formats like GeoJSON and CSV that can benefit heavily from basic compression (see related #747). Ideally we can reuse the code to detect a ZIP file, unpack it in a temporary location, and then return the name/path of the expanded file(s) for processing.