Allow Switching Between Accounts without Logging Out

[jmwright]

This isn't a blocker, just a nice-to-have.

If a user has multiple accounts, it would be nice to be able to easily switch between them without having to log out of one and into another. On GitHub you can switch between organization accounts (and/or personal accounts) with a Dropdown on the web UI. If Stemn-Desktop and the STEMN web UI both had that functionality, it would be easier for users to manage multiple accounts.