Quantity units are too limited on drug orders

I tried to place a drug order with quantity:30, quantityUnits:Tablet(s), and I got this error:

'DrugOrder(100.0161553 of Doxycycline 10 MG/ML Oral Suspension from null to null)' failed to validate with reason: quantityUnits: The units concept must be among allowed concepts

This behavior is wrong.

CIEL includes Dosing unit (162384) and Dispensing units (162402). Arguably this latter should be called Packaging units, but akanter is the authority on this.

Best practice configuration of OpenMRS should be to use these CIEL concepts:

• order.drugDosingUnitsConceptUuid = 162384 (as uuid)
• order.drugDispensingUnitsConceptUuid = 162402 (as uuid)

Given this configuration, drug orders should be allowed to have any concept in either set for quantityUnits.

I propose that org.openmrs.api.impl.OrderService.getDrugDispensingUnits() should return the union of the configured sets.