Inherit APP6 Symbol Set from parent organization

[gjvoosten]

In addition to the Context and Standard Identity, also inherit the Symbol Set from the parent organization.

Closes AB#1184

User changes

• When not explicitly set for an organization, the APP6 Symbol Set is inherited from the parent organization.

Superuser changes

• Superusers can leave the APP6 Symbol Set for an organization empty, in which case it will be inherited from the parent organization.

Admin changes

• None.

System admin changes

• [ ] anet.yml or anet-dictionary.yml needs change
• [x] db needs migration
• [ ] documentation has changed
• [ ] graphql schema has changed

Checklist

• [x] Described the user behavior in PR body
• [x] Referenced/updated all related issues
• [x] commits follow a repo#issue: Title title format and these 7 rules
• [x] commits have a clean history, otherwise PR may be squash-merged
• [ ] Added and/or updated unit tests
• [x] Added and/or updated e2e tests
• [ ] Added and/or updated data migrations
• [ ] Updated documentation
• [x] Resolved all build errors and warnings
• [ ] Opened debt issues for anything not resolved here

[gjvoosten]

But I had to reset all (maybe most) existing organizarions, the app6symbolSet column.

Updated the migration.