Add mechanism that allows module and external code to register custom order number generators - TRUNK-4270

Follow up

Follow up
Updated tests that randomly fail when getting active orders after a revision to wait for a milli second
Applying auto format changes
TRUNK-4276 Changesets that convert units from text to concept should use a file and not a global property

created UpgradeUtil class; moved mapping function

Removed escaping the spaces from the properties file

Removed unused constant for units to concept mappings - TRUNK-4276

Added missing OpenMRS licenses - TRUNK-4276
Renamed GP for next order number seed and set voided by for voided order in test data
Renamed OrderContext.addAttribute to setAttribute and added some debugging lines when getting the order number generator  - TRUNK-4270
TRUNK-4279:  Add DrugValidator and validate drugReferenceMaps from it