Convert thematic_list_comments_arg() to use array arguments

Add filter for using xhtml callback in legacy mode
Convert thematic_comments() and thematic_commentmeta() to html5

Add xhtml callback and childtheme override for xhtml mode
Add tests files for comments and legacy comments
Rename filter list_comments_arg to thematic_list_comments_arg

Correcting a missing namespacing of filter
Rename comments test class to TestLegacyComments

Fix name conflict with test class for standard comments
Merge branch 'develop' into comments-html5

Conflicts:
	library/legacy/legacy.php
Give css class .comment-utility to comment footer

Keep the .comment-meta classes and filters on the
output of thematic_commentmeta(). Do not change any filters
if at all possible
Merge pull request #69 from ThematicTheme/comments-html5

Comments html5