Merge branch 'refine_healpix' into 'NIFTy_8'

demos/re/refine_healpix.py

setup.py

src/re/__init__.py

src/re/forest_util.py

src/re/num.py

src/re/refine/__init__.py

src/re/refine/chart.py

src/re/refine/charted_field.py

src/re/refine/charted_refine.py

src/re/refine/healpix_field.py

src/re/refine/healpix_refine.py

src/re/refine/util.py

test/test_re/test_num.py

test/test_re/test_refine.py

test/test_re/test_refine_healpix.py

test/test_re/test_refine_util.py