Optional Application Settings override for login page

[robertsoniv]

As a demo user, I may want to change the marketplace I am using for the demo. Provide a settings icon button on the login page that opens up a right drawer for them to change the client ID, region, and environment used for login. Eventually this experience may support much more than just switching to other existing marketplaces. We could potentially build the seed CLI into it and allow users to fire up entirely new marketplaces on the fly!