* make sure there is a == and != operator
* remove the 'const' from the non-static const members since they are not default-copiable

BUG: Bugfix for bug 253 (ossim trunk patched likewise, this commit can be safely ignored during the next interal ossim update)

        - Use the VectorDataKeywordlist GetFieldAsInt since they are implemented now
	- Clean commented code, If a method is commented, comment its documentation (with //)
          or the documentation will appear in the SG

ENH : implement SetFieldAsInt and GetFieldAsInt. Add a method copyFieldList. Implement the constructor by copy

      - Implement the methods SetFieldAsInt and GetFieldAsInt to handle
        correctly the fields with int type
      - Implement the constructor by copy since the operator = is implemented
      - Implement CopyFieldList method to be able to copy a field list from a kwl to
        another without copying all the MetaDataDictionary (take as example two vdata in
        different Coordinate systems)