Update database model

[king-michael]

Idea

sim.keywords returns a List[Keywords instead of a query.

Background

When query a sim object, the sim.keywords returned a query. This query could be filtered and executed to become the Keywords. In the most cases this is not needed.

Proposed changes

• sim.keywords -> List[Keywords]
• sim.keywords_query -> query => query.all() -> List[Keywords]
• also change this for sim.children and sim.parents

Todo

• [x] remove .all() from API functions
• [x] change API function which usekeywords.filter(...).all() to keywords_query.filter(...).all()
• [x] check if viewer works
• [x] check if this would be usefull for meta_groups