0.9.0
- Bug: fix file storage new mutation as deleted with put fail error
- Enh #23: extend storage interface with modify
- Enh #56: content hash added to gmail message objects
- Enh #61: separated OAuth token storage - RENEWAL OF OAUTH AUTHENTICATION IS REQUIRED
- Enh #59: Access initialization for gmail e.g. OAuth authentication
- Enh #60: Access check e.g. OAuth authentication