Merge branch 'unified_domain' into 'master'

Unified spaces and field_types into single domain object.

See merge request !46
5 jobs for master in 4 minutes and 35 seconds (queued for 17 minutes and 40 seconds)
Status Name Job ID Coverage
  Test
passed test_min #125691

00:04:13

canceled test_mpi #125692

00:00:22

canceled test_mpi_fftw #125693

canceled test_mpi_fftw_hdf5 #125694

 
  Release
canceled release_image_master #125695