* ui: Use `X-Range` header/meta to decide whether to reconcile or not
Previously we used a `shouldReconcile` method in order to decide whether
a response should trigger a reconciliation of the frontend ember-data
'source of truth' or not. It's a lot nicer/clearer if this 'flag' can be set
alongside the HTTP request information, moreover we almost have the same
functionality in `If-Range`/`Partial Content` HTTP functionality.
Here we partly follow this HTTP semantics but use a custom `X-Range` header
instead.