STY: Change ITK_OVERRIDE for override in whole code (find Modules -type f -exec sed -i 's/ITK_OVERRIDE/override/g' {} +)

BUG: Attempt to fix bug #1482 by avoiding to use the create_generic_raster method which is an in-house addendum to SPTW

(cherry picked from commit a8db8b4c)

This reverts commits:
3d4ab1ff
2dc562e6

Terminate MPI before the end of the main instead of the destructor.
Also clear FFTW threads at the end of DoExecute() not in the destructor.

This reverts commit c7fce23c.