Remove behaviours from Tool model

[AdrianDAlessandro]

Description

Relatively straightforward. We have decided that behaviours should not be in the Tool model. So this PR removes them. The migration removes all instances of them from the database too.

I also noticed that using the Import behaviour in the admin interface allowed for invalid choices for Tool.kind. So I added a clean_fields call to the save method, which has caught that. This will prevent kind being mistakenly assigned to "behaviour" with old data.

Fixes #621

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Technical work (non-breaking, change which is work as part of a new feature)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass (eg. python -m pytest)
• The documentation builds and looks OK (eg. mkdocs serve)
• Pre-commit hooks run successfully (eg. pre-commit run --all-files)

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[Sahil590]

LGTM just tests need fixing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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