At this point we respect any permalink at startup, but we don’t yet
dynamically update the permalink, nor do we respond to ongoing
permalink changes.
The permalink separator being `%00` seems like it might be a bit
controversial. It buys us not having to wrap tiddler titles in double
square brackets if they contain spaces.
Another thing is that this scheme doesn’t support tiddler filters; the
plan is to support them like this:
http://tiddlywiki.com/#!Target%00%00[tag[task]sort[created]]
