fix #1097 proper filter ordering on /tiddlers

This filters out the core bags before any other filters are
applied. I'm not sure why I thought this was ever going to
work the other way. Clearly in a hurry. There's now a test
that helps to make sure right things happen.

*sigh*
release 1.2.21

* properly handle empty but existing HtmlJavascript tiddler
* change title handling in clean1
* add a template macro that puts modified and created in a <time>
* fix filter ordering on /tiddlers