Handle OBX-11 (final, exception, change value) in ORU^R01 HL7 messages

We do not currently consider the OBX-11 value in the ORU^R01 handler. There are several values possible for this, but we really need to focus on:

F: final
X: exception
C: change

TRUNK-1735 will allow us to designate an exception on an observation, so that will be how we handle the X value. F is the normal, expected case. C will be difficult, because it will require finding an existing observation for this HL7 and modifying it. TRUNK-1736 will hopefully provide a mechanism for this.