Features:
* Add a new account.
* Switch accounts.
* Log out of an account.
Also added a cancel button to the login UI which is only shown when a user is adding an account. In that case, the operation should be and is cancellable.
Added a tooltip to the settings button on the landing UI.
Settings button now opens to the (incomplete) settings UI.
Added navigation bar to the settings UI.
Implemented tabbing between settings tabs.
More to come.
