Create universitat-bremen-institut-fur-politikwissenschaft.csl

I started from harvard-institut-fur-praxisforschung-de style by Jonas Bahr and Malte Frackmann and adapted it to the requirements of Institut für Politikwissenschaft (Institute for Political Science) at University of Bremen, Germany. Some of the changes are
- using text-case="title" for nearly all important types of documents
- changing delimiters between authors from ; to /
- discarding quotation marks for titles
- using full author names in bibliography
- setting container name in italic only for journals and newspapers
- adding spechial features for documents with URL like documents and speeches
- modifying the "access" macro in order to state the access more precisely
- avoiding apperance of doi, abbreviation of pages (S.) and name of series in the bibliography