Restructure BodyStructure Location/Qualifier

BodyStructure currently contains:
   location 0..1
   locationQualifier 0..*

Real world usage (from mCODE) indicates that:

    - a bodyStructure without a location isn't meaningful
    - a BodyStructure can consist of multiple locations.  For example, adjacent structures that comprise a single volume with a single planned dose during radiotherapy.
    - it is common practice in cancer registry data to split the qualifier into a laterality qualifier, and a general location qualifier.

Therefore, we propose that the location and locationQualifier fields be eliminated in favor of a backbone element with 0..* cardinality comprising:
     - location 1..1
     - laterality 0..1
     - qualifier 0..*