remove some unused imports. --ch12l000--
new ft for duplicate items. --ch12l001--
test for saving dupe items. --ch09l028--
sanity check can still save same item text on different lists. --ch09l029--
Deliberately wrong uniqueness constraint. --ch09l030--
correct unique_together constrain. --ch09l031--
test list ordering. --ch09l032--
test item string repr. --ch09l033--
implement item string repr. --ch09l034--
implement item ordering by id. --ch09l035--
fix ordering unit test. --ch09l036--
new view test for dupe items. --ch12l014--
Hackish implementation in view. --ch12l015--
New test for existing list form. --ch12l016--

Conflicts:
	lists/tests/test_forms.py
placeholder for ExistingListItemForm --ch09l071--
ExistingListItemForm now inherits from ItemForm. --ch09l072--
Use validate_unique on instance to catch dupes. --ch12l018--
use our new dupe item error constant in tests. --ch12l049--
Change isinstances tests to new form. --ch12l050--
use new ExistingListItemForm in view. --ch12l051--