Added a new plugin mechanism based on Python entry points.

dependencies/normalizers/simulation/band_structure

dependencies/normalizers/simulation/dos

dependencies/normalizers/simulation/soap

dependencies/normalizers/simulation/spectra

dependencies/normalizers/simulation/system

dependencies/normalizers/simulation/workflow

gui/src/components/About.js

gui/src/components/nav/Routes.js

gui/src/components/search/input/InputConfig.js

gui/src/config.js

gui/src/utils.js

gui/tests/env.js

nomad/app/v1/routers/info.py

nomad/cli/dev.py

nomad/config/__init__.py

nomad/config/models/config.py

nomad/config/models/plugins.py

nomad/datamodel/__init__.py

nomad/datamodel/data.py

nomad/datamodel/metainfo/__init__.py