Research work that led to this thesis started almost a decade ago. Naturally, many people were involved in joint research during this time period. A number of them have directly or indirectly contributed to the work presented in this thesis and deserve acknowledgment. First of all, among the current (and former) colleagues in my research group and the various European and German projects through which a significant part of the presented research was funded, I would like to thank Oliver Wäldrich, Philipp Wieder, Angela Rumpl for fruitful fundamental discussions, and (in no particular order)