views/logic: Disable Register button
login: Refactor model and controller logic
middleware: Add wrap-cookies middleware
util: Add environment functions
util: Add header functions
views/error: Show stack trace if debugging
core: Use existing "port" variable
Refactor error pages
Implement support for AJAX login

Issue #233.
js/login: Disable buttons on login

Issue #233.
Refactor middleware handlers to accept request map

This overhauls the application layer logic so that each ring handler now
accepts the request map (and *only* the request map) as its
argument. The reason for this change is that it allows the view layer to
penetrate into the specific request headers, cookies, session etc.

Issue #233.
Implement login and logout functionality

This implements primitive cookie based user sessions, by simply setting
a cookie with the username in it.

Issue #233.
css/variables.less: Fix navbar active link color
Merge branch 'issue/233'