Clean up <br clear="all" style="clear: both;" /> tags.

Clean up <br clear="all" style="clear: both;" /> tags.

This rage was triggered by one in editpage.tmpl which used clear="both",
which is not valid HTML.   Then I figured might as well use a class for them
and make them all consistent.

git-svn-id: svn://svn.code.sf.net/p/phpwiki/code/trunk@2683 96ab9672-09ca-45d6-a79d-3d69d39ca109