Added login, improved registration

A hash of the username is used as the session identifier
Added API endpoint to get items

You can get items that are either a) around you, or b) for a particular
user.
Moved the item table item class into separate file
h3 now has default styling
If the user is signed in, redirect to browser page
Removed unused code, removed z-index assignment
Redirect on load if user auth'd
Save the user's login cookie, forward to browse screen
Updated a line
Added ability to save user info to cookie, navbar changes if user is signed in
Added import of table items
Added user screen