Dynamic header that changes depending on user

[justinarat]

Depending on the user the header/navbar should be different.

• If the user is not logged in, there should be a login link in the header.

• If the user is logged in, there could be a link to their profile or just have their username replace the login link.

• If the user is an admin, the admin link should be visible.

This should be rendered in the server-side.

TODO: If logged out:

• [x] Show logout button instead of login/signup

If logged in (or for users):

• [x] replace "login or signup" link with "logout"
• [x] show make lobby and my lobbies

If Admin:

• [x] Show admin link