Fixed dtype bug in RG-FFT:

If the dtype of the codomain != dtype of result field, information is lost due to conversion complex -> float.
5 jobs for master in 40 minutes and 28 seconds (queued for 22 minutes and 50 seconds)
Status Name Job ID Coverage
  Test
passed test_min #118771

00:04:15

passed test_mpi #118772

00:07:21

passed test_mpi_fftw #118773

00:08:39

passed test_mpi_fftw_hdf5 #118774

00:10:06

 
  Release
passed release_image_master #118775

00:18:44