Consider including support for common widely distributed types (specifically GeoJSON)

[mglazer]

What happened?

The only way to use GeoJSON types with Conjure right now is to use an external type. In Java, since we still have external types, this works out ok, however, with Javascript, this just becomes any, which means a typecast is immediately necessary.

What did you want to happen?

It would be nice if Conjure had support for some small set of external types that we can completely define inside of any language, and then let us bring those in, similar to how XML has XML Schema imports.