Clarify required fields on management interfaces - TRUNK-377

Switched to calling errors.globalErrorCount instead of errors.hasGlobalErrors() - TRUNK-377

Conflicts:
	api/src/main/java/org/openmrs/validator/ImplementationIdValidator.java
	api/src/test/java/org/openmrs/validator/ImplementationIdValidatorTest.java
	webapp/src/main/webapp/WEB-INF/messages.properties