* introduce legacy generators
* introduce generator navigation service
* Introduce default options. These accept a userId so that they can be policy-defined
* replace `GeneratorOptions` with backwards compatible `GeneratorNavigation`
* introduce `GeneratorHistoryService` abstraction
* implement generator history service with `LocalGeneratorHistoryService`
* cache decrypted data using `ReplaySubject` instead of `DerivedState`
* move Jsonification from `DataPacker` to `SecretClassifier` because the classifier
is the only component that has full type information. The data packer still handles
stringification.
