API should assign order type for drug and test orders if not specified

If a DrugOrder or TestOrder is saved with no order type and the concept is not mapped to any specific order type, the API should set it to 'Drug order' type or 'Test order' respectively as the default.

Dev Notes

• Write a unit tests first, should be failing initially
• Add constants for drug and test order type uuids which are 131168f4-15f5-102d-96e4-000c29c2a5d7, 52a447d3-a64a-11e3-9aeb-50e549534c5e respectively