Add class to track case/domain mapping
Refactor model
Make the case/domain mapping more generic
Merge branch 'master' into case-domain-map
Make tests pass again
Move StockState to core hq
Merge branch 'master' into case-domain-map

Conflicts:
	casexml/apps/stock/models.py
	casexml/apps/stock/tests/test_stock_state.py
Merge pull request #192 from dimagi/case-domain-map

Add class to track case/domain mapping