Add logout button

[alanpoon]

1. Currently there is no logout button
2. User need to manually delete session file in order to change account

To do: Add temporary logout button above the setting button or wait for the setting page completed.

[kevinaboos]

Agree this is nice to have.

Should logging out of a session cause that session file to be deleted? I would think that users don't expect their session to be deleted upon logging out. For that, we can have a separate button that deletes a session (I think other clients call this "Wipe cache", but we can do it in a more fine-grained fashion that allows a user to delete specific saved sessions)

[kevinaboos]

Adding ways to manage local sessions on disk is part of Stage 2 milestone, not stage 1. We should separate that out into a separate issue.

[Guocork]

I'll take care of this task. Please assign the issue to me.

[kevinaboos]

Great, thanks so much!