Update beck-online.js

1. beck-online.js
Added support for beck-online "Leitsatzkartei" LSK (database of leading records), i.e. scraping of articles where beck-online does not have the article itself but only information about the article

2. juris
Added new translator for the German legal database Juris.
while you're at it, might as well make sure it's a 4 digit date with `/\b\d{4}\b/` (i.e. \b for word boundaries) and drop the 'g' flag, since you're not using more than one date from the match anyway.