Improvements :\n -Automatic management of redistribute waitings in destination operators.\n -Redistribute transfers (MPI and OpenCL) could be seperated along vector components.\n -OpenCL kernels events use to synchronize GPU computations. \n -Examples update.

Handle data transfers from/to devices within the Redistribute class. Update examples. Update gpu benchmarks

Update differential_operations and stretching (fix bug + optimizations) - Add GlobalTests (test functionnalities, perf ...)

fix some bugs in stretching operator/differential operator + add finite differences validation for TG benchmark + add some problems in Examples