application lifecycle

Dependency injection
- Services registered with LifecycleManager
- Hooks for adding/removing contacts registered with ContactManager
- Hooks for adding/removing identities registered with IdentityManager
Sign in
- User enters password
- Password used to decrypt database key
Database opened
Services started
- PluginManager creates and starts plugins
Main user interface shown
Sign out
Services stopped
Executors shut down
Database closed
Shutdown hooks run (not guaranteed)