Pass collection options consistently

We recognized, that our collection was getting initialized multiple times with inconsistent options. The reason for this is, that there are different methods that do the preparation of the options:

- App.bootstrapData() -> getModelForSpec merged the spec params directly into the options
- App.start() -> Fetcher.hydrate() didn't merge the spec params

We refactored parts of the Fetcher class and added the merging to the hydrate method.