Also, apart from the config value concept being quite hacky already, after removing `{data: false}` as possible config for a path, we're left with one of `false`, `"seen"` or `{data: true}` as value for a path cache setting. That doesn't make sense from a high-level point of view and seems to be just a relic of tacking more than `true` and `false` in there without migrating to a saner structure.

It's also less than optimal having to use `remoteStorage.caching.SEEN` (or either of the above values) as an argument when calling that method instead of something clean like just `seen` or `flush` for example.