Simplify non-active user page

Simplify non-active user page

Currently, the logic of whether a user account has been activated is in
the main user.html template. This is not good as: doing that check for all
users from template code is probably not great for performance, but more
severly, the template logic is rather difficult and convoluted.

Split this in a user.html and a user_nonactive.html where user.html is
used for active users and user_nonactive displays all the "you still need
to be activated" blurbs. This makes the templates much easier on the eyes.