Primo: make data extraction slightly more general

Now tested locally. Also added some comments etc.
I have seen in your example that you want to replace for example "circa" and some date range. However, the regexp could potentially match some other stuff as well and I feel it would never be complete (if we think about different languages etc.). I could imagine to delete everything in parenthesis for the creator's name (and we should treat the contibutor then the same), but I haven't made my mind if that would be always a good idea...