Add more lifecycle states, merge lifecycle events.

...g/briarproject/bramble/api/db/DatabaseMigrationEvent.java

.../briarproject/bramble/api/lifecycle/LifecycleManager.java

...arproject/bramble/api/lifecycle/event/LifecycleEvent.java

...iarproject/bramble/api/lifecycle/event/ShutdownEvent.java

...riarproject/bramble/api/lifecycle/event/StartupEvent.java

.../briarproject/bramble/lifecycle/LifecycleManagerImpl.java

.../org/briarproject/bramble/sync/DuplexOutgoingSession.java

...n/java/org/briarproject/bramble/sync/IncomingSession.java

...org/briarproject/bramble/sync/SimplexOutgoingSession.java

...riarproject/briar/android/login/OpenDatabaseActivity.java