LMSpace and PowerSpace fixes

- Fix serialization, total_volume and weight methods/properties in
PowerSpace
- Fix copy in LMSpace
4 jobs for space_fixes in 24 minutes and 54 seconds (queued for 2 minutes and 13 seconds)
Status Name Job ID Coverage
  Test
passed test_min #129430

00:07:20

passed test_mpi #129431

00:13:30

passed test_mpi_fftw #129432

00:15:13

passed test_mpi_fftw_hdf5 #129433

00:16:40

27.0%