Improve SDK

- [x] Allow more flexibility to configure guzzle cache plugin
- [x] Use virtual proxies, to remove dependency to entity manager in entities, like doctrine
- [x] Use annotations to describe mapping to the API fields like doctrine
- [x] Redo hydration to get the benefit of proxies and annotation
- [x] Handle /me route
- [x] Add User entity
- [x] Handle new labels properties
- [x] Handle extended API object graph
- [x] Unit tests
- [x] Changelog

**Improvement**

- Fetch
  - 100 records (without extends feature) : ~18 sec
  - 100 records (with extends feature) : ~2 sec
- Hydration
  - Time spent to hydrate object remains approximatively the same, but is now more robuste and extendable
with annotations
- Plugins
  - Cache plugin is now fully configurable
- Entities
  - Dependency to EntityManger for entities has been removed :yum: