WIP new frontend

Initial refactor: badger -> gravel

Add new PersistentObjectActions API

Add ExecuteQueryOptions

Add example config

Remove StartTime from App

move internal actions to own files

tidy

Split up database logic from Service

Rename Object to PersistentObject

Reorganize

fix type alias for AttributeVisibility

Add FileSystemStore for users

Remove poorly implemented hooks

Remove AuthHandler

Remove virtual attributes from example-postgres

move user code to own package

Move handlers from user_account.go to badger.go

Remove JsonUserStore

Add initial AuthHandler