change the datatype of the variable numberOfNodes aka numberOfLBnodes (fka size_Mat) to unsigned long long ... with respect to large grids (>100e^6 Nodes per Level) ... in this regard the 27 directions are changed to size_t and some control variables are also changed to size_t

set source file props of tests to LANGUAGE CUDA

Related to #37

Moved Simulation::init() to Constructor, Simulation:free() to destructor and exchanged some members of Simulation with unique_ptr instances.