RESTWS-623 Make RestServiceImpl.getResourceByName testable
* add dependency for OpenmrsClassScanner to RestServiceImpl and inject via xml
using the factory method on OpenmrsClassScanner.getInstance() which returns the
singleton instance
* add helper method to RestServiceImplTest to set the current openmrs
version for tests
* add fake/test package in omod-common/src/test/java/org/mockingbird/test/rest/resource
with fake Resource/SubResources for testing purposes so they do not
influence other tests since classes on org.openmrs classpath get loaded
by OpenmrsClassScanner
* add tests for getResourceByName by mocking the
OpenmrsClassScanner.getClasses
