* Written nGraph reference for the operation RDFT.
* Used std::reverse() algorithm to simplify the function reverse_shape() from fft_common.cpp.
* Added assert into the function offset_from_coords_and_strides().
* Deleted redundant variable.
* Deleted redundant functions from the reference implementation of (I)DFT.
* Renamed the method reverse_shape() in fft_common.hpp.
* Code style fix.
Vladimir Gavrilov