Fix dynamic load balancing (initial working version)

CMakeLists.txt

examples/modular/sd_4.cpp

examples/whole-program-generation/spring_dashpot.py

runtime/boundary_weights.cpp

runtime/boundary_weights.cu

runtime/boundary_weights.hpp

runtime/contact_property.hpp

runtime/dem_sc_grid.cpp

runtime/devices/cuda.cu

runtime/devices/device.hpp

runtime/domain/ParticleDataHandling.hpp

runtime/domain/block_forest.cpp

runtime/domain/block_forest.hpp

runtime/domain/domain_partitioning.hpp

runtime/domain/regular_6d_stencil.cpp

runtime/domain/regular_6d_stencil.hpp

runtime/pairs.cpp

runtime/pairs.hpp

runtime/pairs_common.hpp

runtime/property.hpp