BUG FIX: for the shared memory beta kernel, threads running on cells with GHOS_LAYER flag
should countinue to the end of the kernel code since they load/save data to shared
memory which will be used by other threads.
Added the simulationStep{Alpha/Beta}Rect functions. These functions are
used to run the Alpha/beta operations on a rectangular part of the
domain.
rectangular beta kernel does not need to return for ghost layer cells
Added the ability to run the synchronization functions in each direction
separately.
fixed conflicts