Greatly improves the user interface of decompose_mpi.f90

Adds an option -a for oneTwo-only mode, which is not implemented, yet.
Adds -nosd option to decompose_mpi for one-two only mode
Uses FFTW in -nosd mode (one-two only mode)!
Statically links the FFTW library in Makefile.ifort
Merge branch '12only'