Seed data consistently

- App seeds quota definitions, stacks, domains & organizations
- SpecEnvironment used to only seed quota definitions
- DatabaseIsolation::TruncateTables would seed quota defs and stacks
- Now all 3 places uses Seeds.write_seed_data
- Particular domains and orgs depend on the config used

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>