3.4 oracle sdo improvements

While working on deegree services on top of an Oracle database we encountered rare crashes in the sdo converter during data retrieval.

Eventually we discovered that it is allowed by the sdo specification to have polygons which are defined as a combination of compound rings and simple rings. This case was not properly handled by deegree. Most sdo exporters do not typically generate these types of polygons, but our database happened to contain them.

This pull requests contains changes that improve the parsing of sdo polygons to include support for this combination of compound and simple rings. It also contains changes to improve handling of rings of unknown type (= deprecated, but still supported).

I've created a few unit tests based on sdo geometries we encountered in our database. Currently we still have limited overall test coverage for this part of deegree. It would be a good thing to strive for 100% coverage for the sdo converter to ensure that we are able to properly handle any valid sdo correctly.