Added metainfo and normalization for DOS, compressed test files, added regtests for DOS.

nomad/metainfo/encyclopedia.py

nomad/normalizing/encyclopedia.py

...ormalizers/band_structure/polarized_gap/vasprun.xml.bands

...alizers/band_structure/polarized_gap/vasprun.xml.bands.xz

...alizers/band_structure/polarized_no_gap/vasprun.xml.bands

...zers/band_structure/polarized_no_gap/vasprun.xml.bands.xz

...malizers/band_structure/unpolarized_gap/vasprun.xml.bands

...izers/band_structure/unpolarized_gap/vasprun.xml.bands.xz

...izers/band_structure/unpolarized_no_gap/vasprun.xml.bands

...rs/band_structure/unpolarized_no_gap/vasprun.xml.bands.xz

...data/normalizers/dos/polarized_vasp/vasprun.xml.relax2.xz

tests/data/normalizers/dos/unpolarized_vasp/vasprun.xml.xz

tests/normalizing/conftest.py

tests/normalizing/test_encyclopedia.py