Merge branch 'release/0.50.2' into develop
parallel: add chunk size option (untested)
streamlines: add option to auto discover # of cpus
implement Circle seed generator
automagically set contour levels from lin/log plot_opts
propagate pretty_name to sliced fields
streamlines: default ds0 is now sensible; oops
enable easier overriding of topology color mapping
add default_verb to viscid common argparse
refactor np -> nprocs in vlab.multiplot
add follow_fluid to vlab
remove newline from multiplot's suptitle

it was looking weird in p2d's animations
fix typeos in xdmf reader
change order of arguments for circle seed gererator
refactor relative imports to absolute imports
p2d better nan feedback
Merge commit '2127ee45ab9ff209d9114825beb3cc7dd50f12c5' as 'doc/_themes/sphinx_rtd_theme'
Squashed 'doc/_themes/sphinx_rtd_theme/' content from commit aa0d6f7

git-subtree-dir: doc/_themes/sphinx_rtd_theme
git-subtree-split: aa0d6f7abd0efda41565bdeb12a3ed303d5e584c
return root_seeds after following fluid

useful for daisy chaining follow_fluid calls?
fix 1d plotting from p2d