Added UniqueID class, and support for UInt64 properties

CMakeLists.txt

data/planes.input

examples/dem_sd.py

examples/main.cpp

runtime/contact_property.hpp

runtime/copper_fcc_lattice.cpp

runtime/copper_fcc_lattice.hpp

runtime/create_body.cpp

runtime/create_body.hpp

runtime/dem_sc_grid.cpp

runtime/dem_sc_grid.hpp

runtime/domain/ParticleDataHandling.hpp

runtime/pairs.hpp

runtime/pairs_common.hpp

runtime/property.hpp

runtime/read_from_file.cpp

runtime/read_from_file.hpp

runtime/unique_id.hpp

src/pairs/code_gen/cgen.py

src/pairs/ir/types.py