some minor Optimizations and fixing some memory leaks
Implemented set flags and density functions by exploiting the function
clEnqueueWriteRect of OpenCL 1.2
Implemented store flags and density functions by exploiting the function
clEnqueueReadRect of OpenCL 1.2
BUG FIX: Using appropriate MPI Data type for single and double precision
GPU values.
Added the feature to read the simulation configuration data from an xml
configuration file.