Set a modifier on the SiteInfo tiddler

Otherwise it can throw errors later.
Add links to / and /tiddlers both in friendlytiddler.html

We need both as they are different.
Simple and clean presentation for friendlytiddlers

We filter the tiddlers being sent to be just those tiddlers
which are not from core bags and sort them by -modified.

This results in a more relevant list of tiddlers being
passed to the template.