templatefilters: use templatefilter to mark a function as template filter
Using decorator can localize changes for adding (or removing) a
template filter function in source code.
This patch also removes leading ":FILTER:" part in help document of
each filters, because using templatefilter makes it useless.
This patch uses not 'filter' but 'templatefilter' as a decorator name,
because the former name hides Python built-in one, even though the
latter is a little redundant in 'templatefilters.py'.
<script type="text/javascript">process_dates()</script>
{motd}
</body>
</html>