TRUNK-4307: Added error message in implementation id form

Added validator for ImplementationId.java, ImplementationIdValidator.java,
so that validation can be conducted all at once and then reported back to the user.

Added OpenMRS lincense and @should for unit test
 MarshallException while trying to create an Encounter - TRUNK-4248
author:lluismf
Merge pull request #1033 from geoff-wasilwa/TRUNK-4307

TRUNK-4307: Added error message in implementation id form