RA-343: Include Process HL7 task

https://issues.openmrs.org/browse/RA-343

Added a method that adds Process HL7 task when module is started.
Just FYI, this would be an appropriate place to introduce a ReferenceApplicationActivatorTest class (that is not context-sensitive) and uses and mock of SchedulerService to ensure the right method was called.

(You don't actually have to do this.)