Switch login/signup to profile/logout in new header when logged in #18
Description
Currently, the new bootstrap 4 toolbar used on the homepage/sponsors/volunteers page doesn't vary its login/signup links to reflect your logged-in status, but the homepage is where you usually get redirected after logging in, so it creates a very confusing infinite "login" loop:
Whereas, from any other page there's a logged-in version of the toolbar:
This template: https://github.com/CodeForPhilly/codeforphilly.org/blob/develop/html-templates/designs/site-bootstrap4.tpl#L73
Needs to have an if/else added like the old template has: https://github.com/CodeForPhilly/laddr/blob/develop/html-templates/includes/site.header.tpl#L32
To switch to showing a bootstrap4-ified version of what the login and signup buttons should be replaced with for logged-in users (e.g. a logout button and a link to their profile) -- maybe or maybe not set up with a submenu like the old ones used