title: Sembast best way to remove all documents
body: <p>I'm using Sembast in a Flutter app. I have to refresh all the data in a store and need a way to removeall documents in a store. I looked at the API and only way I can see is either to get all keys and use them in a finder to delete them or drop the store and recreate it. Not sure if I overlooked something to support this?</p>