Add scroll to bottom and scroll to top to top-right and bottom-right

This is mainly for mobile. In a long topic, there is no easy way to
scroll to bottom without tiresome manual scrolling. The new button
on top right of all pages now acts as a scroller, when user tap
on it he will be sent directly to bottom of page. The reverse
equivalent is added in bottom right to page header.

Per request: https://fanboi.ch/lounge/1/42-71
Initial auto-link implementation.

Any text input begins with http:// will now be auto-linked. Input
are sanitized using Python 3 port of Werkzeug's werkzeug.urls.url_fix
and html.parse.

Per request: https://fanboi.ch/lounge/1/71