FeatureCollection and Feature wrappers are not fleshed out

[asinghvi17]

For example, it's pretty hard to actually get features out of a Wrappers.FeatureCollection. You have to monkey around a bit, and access fc.parent[i].parent.$feature_name.

It would be nice to let FeatureCollections subscribe to the Tables.jl interface and let Feature objects be getproperty'ed.

What do people here think? It could even be an extension on Tables.jl so as to not add a dependency.

[rafaqz]

The idea is to use feature = GI.getfeature(fc, i) and GI.geometry(feature)/GI.properties(feature).

Best to never access fields so that eg. a GeoJSON.jl Feature will also work with the same code.