Minor refactor and add lots of documentation.

brian_dashboard_manager/grafana/dashboard.py

brian_dashboard_manager/grafana/datasource.py

brian_dashboard_manager/grafana/folder.py

brian_dashboard_manager/grafana/organization.py

brian_dashboard_manager/grafana/provision.py

brian_dashboard_manager/inventory_provider/interfaces.py

brian_dashboard_manager/routes/update.py

brian_dashboard_manager/templating/eumetsat.py

brian_dashboard_manager/templating/gws.py

brian_dashboard_manager/templating/helpers.py

brian_dashboard_manager/templating/render.py