Permit restoring an existing session after browser refresh

[niloc132]

As a user who sometimes encounters errors in the Web UI, I occasionally refresh the page and expect my existing session to remain active.

This is more of a concern now with anonymous access being disabled in an upcoming release - rather than authenticate again, the dh.CoreClient fires a EVENT_REFRESH_TOKEN_UPDATED event with a token that can be stored, and for a limited time, used to reconnect to the same session. That token can either be passed to dh.CoreClient.relogin() (matching DHE's behavior), or the string in its bytes field passed to login(), with type set to Bearer.