Make a wrapper IFeatureCollection implementation of IDictionary<Type,Object> that switches on well-known interface types

[halter73]

We could do something similar to what @loudej did for the Kestrel header dictionaries for FeatureCollection.

[Tratcher]

Yes. Note that #339 proposes restricting the surface area down from a full IDictionary, so this shouldn't be nearly as complicated as the header collections.

[Tratcher]

Oh, and this shouldn't be a wrapper around IFeatureCollection, it should be done in the default FeatureCollection implementation.

[glennc]

Backlog unless this becomes more important for overall perf work.

[davidfowl]

We do this in each server already