Allow implementations to control whether drug orders require formulation TRUNK-4440

Follow up to address review comments  - TRUNK-4440

Conflicts:
	api/src/main/java/org/openmrs/util/OpenmrsConstants.java
Cleaned up javadocs, code in Order, DrugOrder classes and corrected typo in test data file name

Cleaned up javadocs, code in Order, DrugOrder classes and corrected typo in test data file name

Cleaned up javadocs, code in Order, DrugOrder classes and corrected typo in test data file name