Detect missing oids before parsing QDM elements, raises exception if found
Update error message to align with MAT terminology, remove ids from message
Update unit test for updated error message
Move 1.1.1.1 into UNDEFINED_OID
Merge pull request #3 from projecttacoma/detect_missing_oids

Detect missing oids before parsing QDM elements
Functional manual variable parsing and data criteria generation
Update subTree variable flag to qdmVariable to align with MAT
Move variable parsing to sub_tree level, handle data criteria variables
Clone data criteria using Marshal to fix tests
Merge pull request #4 from projecttacoma/manual_variable_support

Add support for Variable subtrees
Add support for converting AGE_AT to patient birthdate
Update AGE_AT handling to create precondition and data criteria from Utilities