Merge remote-tracking branch 'nest-master/master' into nest-master

# Conflicts:
#	models/correlomatrix_detector.cpp
#	nestkernel/connection_manager.cpp
#	nestkernel/model_manager.cpp
#	nestkernel/model_manager.h
#	nestkernel/nest.cpp
#	nestkernel/node_manager.cpp
#	nestkernel/simulation_manager.cpp
#	nestkernel/source_table.cpp
#	nestkernel/sp_manager.cpp
#	nestkernel/spatial.cpp
#	nestkernel/target_identifier.h

Author: JanVogelsang