fix semantic page links and attributes, esp. attributes. they get stored as link...

fix semantic page links and attributes, esp. attributes. they get stored as link to empty page also. tighten semantic url expander regex, omit want_content if not necessary

git-svn-id: svn://svn.code.sf.net/p/phpwiki/code/trunk@5258 96ab9672-09ca-45d6-a79d-3d69d39ca109