Migrate categories from assets to asset models

- Create category field with relation to asset categories model
- Replace power_consumption column from assets to asset models
- Replace place_of_collocation column from assets to asset models
- Update tests
- Add script to migrate categories from assets to asset models
Merge branch 'feature/add-power-consumption-and-place-of-collocation' of https://github.com/kula1922/ralph_assets into feature/add-power-consumption-and-place-of-collocation

Conflicts:
	src/ralph_assets/models_assets.py