Use Feature<TGeometry, TProps> when constructing FeatureCollection?

[wagich]

Using the default Feature class, the properties get converted to a Dictionary<string, object> before the class is serialized which makes all the property names identical to their .NET versions and circumvents any JSON serialization conventions.

I thought I could use the generic version Feature<TGeometry, TProps> to get full serialization of my property object, but unfortunately FeatureCollection only accepts the subclass Feature (which is a Feature<TGeometry, Dictionary<string, object>>. Is there a specific reason for this?

[YaroslavKormushyn]

Implemented by #160.