Extension to tiddlyweb select filters to use relative time statements.

Where a filter is:

    select=modifier:>2011

once could expect either a tiddlywiki timestamp string, a fragment
thereof, or some numbers that end with 'd', 's', 'm', 'h', 'y' (case
insensitive) meaning Days, Seconds, Minutes, Hours, Years. We don't
worry about months. If the trailing letter is there, we translate it
into an absolute time in the past, relative to now.

This makes it possible select things like "everything modified in the
last day".

Copyright 2011, Chris Dent <cdent@peermore.com>

BSD License
