Merge pull request #1 from jlkeiper/master

DRUGHIST-2 - Confirmed
Populated DrugEvent class with fields and generated setters and getters.
Created DrugEventType enumeration.
Added method to DrugEventService and DrugEventServiceImpl
DrugEvent and DrugEventType enumeration created
Added hibernate mapping file & liquibase changesets for DrugEvent class
Started implementing data access layer and Service API
Added constructors to drug event class
Implemented all methods in DrugEventHibernateDAO