Merge branch 'minimizer_tweaks' into 'master'

simplify descent minimization

See merge request !183
6 jobs for master in 25 minutes and 19 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #246606
test_min

00:04:19

passed #246607
test_mpi

00:07:40

passed #246608
test_mpi_fftw

00:08:35

passed #246632
test_mpi_fftw_hdf5

00:10:42

64.0%
failed #246609
test_mpi_fftw_hdf5

00:09:15

 
  Release
passed #246610
release_image_master

00:06:01