Added the new implementation of store function which utilize the opencl device buffer copy
BUG FIX: clEnqueueCopyBuffer command needs an explicit barrier to guarantee to be finished
Added the test for blockwise storing of cell flags values
Added the new implementation of store function for density distribution values  which utilize the opencl device buffer copy
BUG FIX: offset for clEnqueueCopyBuffer commands should be in bytes
BUG FIX: flags and density distribution test were wrong
Added the blockwise set functions and corresponding tests for velocity, flags, density(distribution) values