* The notification-count style is only needed if you are logged
in. Given a small percentage of our users are logged in, we
load a lot of render blocking css unnecessarily.
* The bell icon is not needed for anonymous users so pull that
out from skins.minerva.icons.images which is loaded for all users
into a module only used by logged in users (skins.minerva.icons.loggedin)
* Simplify the user-button rule - it is overly specific - probably for
historic reasons.
Additional changes:
* Simplify isAuthenticated helper
Change-Id: Ia72e7e45d276e8aac1ff5471bf6158705c7b5f99
