Aura web config consolidation

This MR is based on #259 (closed)

Done

• The folder config/aura-web/fixtures/custom is tracked by git: It is not tracked anymore
• Consolidate the config structure (fixtures, steering folder): Aura Web now has a fixtures and a fixtures/sample folder only.
• As part of the release, all fixtures in fixtures/sample are updated from the version provided in Steering. To do so call the new make target make dev.clone-fixtures.
• Now there is a command $ make aura-web.fixture to import fixtures. There is no more differentiation between sample, test, program and others, since there is no added benefit for end users when splitting things up. Instead fixtures and their meaning are described in the docs. The docs also outline if fixtures are required for a functional UI.
• The current documentation on production settings, advises to create a file /app/steering/production_settings.py and fill it with example code. It contradicts with the existing file under config/services/steering.py. I'm assuming it is the same as the current sample Python file. It is yet another approach to the existing logic: Currently we store all the more detailed service specific config options in the config/services/ folder. Only Steering and Tank don't support this approach yet fully. Compare the discussion here and the Docker Compose config comments there. I've performed following changes:
  • config/aura-web/settings-production.yml is now pointing to ../services/steering.py`
  • the folder config/aura-web/steering is removed
  • the sample config in config/services/sample/steering.py is updated with the current contents from the docs.
  • The documentation on "production settings" got simplified and being more explicit on "LDAP config"
• The additional config argument steering-production.yml should not be required. Aura Web should use production settings by default. Therefore there should be no need to have extra argument for the most common use case. This can be solved by Optionally load advanced configuration file fro... (steering#190)
• Clarify the need for an additional docker-compose.steering.yml --> it turned out it's for @eigenwijsje's Steering dev purposes.
• End users should not be instructed to edit or write Python code nor reading technical Python Framework documentation as outlined in the documentation. According to exchange with @eigenwijsje it is not easy in Django to provide a way to configure advanced things like LDAP via YAML config files. Therefore I suggest to at least provide working code samples for the most common use cases (e.g. LDAP connectivity). YAML config can be re-evaluated post-1.0. Ticket: Docs: Explain how to configure LDAP using the p... (#289)