Add two functions: tagger_url() and tags_list()

I don't know how these methods can be included in my previos plagin "Tagger" in order to call them for any page of the site. So I desided to place them in "FrontPage".
tagger_url() retuns url of the page with type "tagger".
tags_list() retuns string consisted from links to pages with list of pages selected by some tag.

Example script for layouts to display tags (with links) of the page:
<p><?php echo $this->tags_list($this->tags()); ?></p>