Major new feature: User Dashboard.

Long time... this adds support for a fully customizable, widget-driven
user dashboard.  A user's dashboard is viewed directly from the root
page when logged in.  On the dashboard, click 'configure' to add /
remove / resize / move widgets around.
Minor fixes & cleanups to dashboard.

Don't crash if user has not yet visited their dashboard.  Minor fixes to
existing widget placeholders to make them a bit readable.
/photos/ now goes to user's stream if logged in.