Move guts of code in cmd in to application/FOO.go packages

[thisisaaronland]

Make it easy for people to roll their own tools with custom writers, readers or other instances that use a URI-based syntax.

Something like:

package main

import (
            _ "github.com/my-org/my-writer-repo"
)

import (
            "context"
            "github.com/whosonfirst/go-whosonfirst-exportify/application"
)

func main() {

           // something something something flags TBD something something
           app := application.NewAsFeatureCollectionApplication(ctx)
           app.Run(ctx)
}