fixed tests. removed old migrations files and created new initial
incremented version
changed creation of bid basket item
incremented version
removed is_locked from biditem. incremented version #
bid basket item method is_locked now calls lot.is_locked property. is_locked property on lot is meant to be overridden
added ability to extend biditem
fixed BaseBidItem (abstract base class) foreign key related names
fixed various issues with abstract classes.
Merge pull request #5 from curlee/master

Lots of improvements over previous versions.