Cleanup: removed dead CSS
Profile: moved detailed statistics to a separate page

This page is now only accessible by the user itself and administrators.

Fixes #211.
Scores: allowed retrieving all top scorers
Last action: be explicit in which context it's adjusted
Buttons: ensure button colors persist for anchors
Profile: display user properties and latest activity

This is a complete revamp of the public profile page which includes all
new public-facing properties and last activity status, as well as the
position in the language a user has contributed the most during the last
30 days.

Fixes #212.
Cleanup: moved navbar-related CSS into a separate file
Navbar: switch to `nav` tag
Cleanup: use `background-color` instead of `background`
Navbar: also highlight on focus
Profile: moved user navbar items to a drop-down

Fixes #214.