Fixed error output when headers have already been sent
Updated comment
Removed old code
Implemented type validation and relation access on Record

- Included property to toggle type validation on Object
- Added interface to get and set validation on Schema
- Added function to validate a value for a property using the Schema
- Added validations to default property types
- Set validations for relations on Record
- Fetch related from Record::offsetGet()
Added OO interface for output control
Included some missing exception classes