TODOs

A list of things that could or should be done. Contributions are welcome.

• introduce hasField() method on Module instead of having to use getValue() and catching an InvalidFieldException?
• AggregateField and ReferenceField are not tracked with ChangeEvents?
• fix unspecific documentation in various files (verbose copy&paste docs)
• improve existing validation system/hooks
  • add stable validators
  • maybe reuse Agavi/Symfony validators?
  • validation options instead of new fields with specific validators?
• remove *Collection fields?
• more tests