STSM: added paginator bar
stsm: dont forget query + searchmodel after search

but reset after closing the view
stsm: first version of paginator with ToDos

TODOs:
- only show available pages
- parallel using of recommender and search engine will probably produce expections --> close one when the other is started
- general testing and bug fixing
stsm: safe casting (close one, open other retriever)
stsm: various fixes and refactorings

- always send the set-id if available
stsm: fixed NPE for DocumentRetrievalController