Accept more input formats

[felix-schott]

Description

Currently the ob get_buildings utility and the underlying download_buildings.download() function accept a GeoJSON AOI, either as a file or piped from stdin. As WKT is already used under the hood, it makes sense to also accept WKT as an alternative to GeoJSON. It's easy to distinguish between both even when piped in.

Other formats could also be supported, potentially the full range of formats that is supported as output formats.

[mtravis]

I think having the ability to directly pass the WKT is a great idea.

[cholmes]

Love it, and more formats would be interesting. Related is #13 (comment) - I think we also need to tighten up what happens if a user passes in a geojson (or other format) with more than one feature. And also what we do if someone puts in a point or a line. Like might be nice to just apply some standard buffer, and also a flag to control buffer size.