Update Juristische Zitierweise according to Stüber

I just looked at the citations and not (yet) at the bibliography. This should fix #1046 and several other small improvements:
* work with groups for better handling of punctation
* use of label locator
* seperate several authors with "/", i.e. delete a space
* macro locator-with-label, firstpage-locator
* split macro autor-note into autor-note (only authors), autor-editor-note
* introduce et-al when there are more than two authors/editors
* add legal case