* no longer using IField as a zope interface, just have a Field class now
* IntField now has auto_increment property
* general work on ForeignKey fields, still not happy with implementation
* ForeignKey validation during save/load
* Fields now have more properties, links to model and meta class parents
* refactoring around how Model instances are created
* Query returns copies of Model instances
* Query speeds and Manager.get() are now faster
* general refactorings