Add logout and key buttons

[gjwgit]

Description

Add a logout/login button and key button

If user is not logged in then show the logout button, else the login button. Action is then the appropriate solidui/solidpod call to login to a solid server or to logout from that server.

For the key button this will popup the show key dialog.

Why

So that as a user I can logout from the solid server and then log in to a different account/server.

Closing Criteria

Checklist for closing the issue:

• No errors from make prep
• All tests pass make qtest
• Can logout
• Can login
• can show the key/change key through the popup

Alternatives

Currently there is no way to logout or change the key. An alternative is to use the SolidScaffold default bottom bar but that is perhaps too heavy for the app for now.

Additional Context

Probably use Icons.login, Icons.logout and Icons.key