set all memory size parameters when creating buffers to size_t, to avoid problems for very big data sets. added some exception handling, but currently all openCL errors connected to a graphic drivers reset seem to crash mitk either way. setting the lower or upper slice bound updates now the other. made apodisation arrays persistant to avoid unneccesary recalculations.
Signed-off-by: Franz Sattler <sattler@ad.dkfz-heidelberg.de>