prevent markdown parser from auto-converting inline link text. refs #389
prevent markdown parser from auto-converting inline link text. refs #389

the markdown parser auto-converts inline text in links. unfortunately
this triggers our tag and group reference processors and therefor
creates nested links. in order to support inline tags in links with
proper markup we separately convert the provided link text as markdown,
clean the generated content and reassigned the cleaned content as
element tree.

stadtgestalten/stadtgestalten,stadtgestalten/stadtgestalten,stadtgestalten/stadtgestalten