[NTG-context] Add a headrule to the header and reduzie interlinespacing in narrower

Hi, I have two problems. Firstly, I'd like to insert a headrule in textwidht under the headertext and secondly I am using the narrower-environement for citation, but instead of big interlinespace I'd prefer medium interlinespace for the citation. Probably it is the wrong way to use narrower for citations, what would be better? Further it would be fine, if I could disable indenting in the citations. Kind regards and thanks in advance Bert