Introduced SGRefObject (pulling refcounting out of CSGObject)
Refcounting in StructuredLabels
Class CStructuredData does now extend SGRefObject instead of CSGObject
* Renamed CStructuredData to StructuredData.
* Need to removed the "C" in CFactorGraphObservation, CSequence and CRealNumber, because they
  do not know how to serialize.
* Fixed unit tests/examples to reflect new names.
* Added basic test for RealNumber labels.
Updated class names in SWIG mapping.
Putting refcounting from SGObject to new super class SGRefObject.
Fix libshogun example (preventing segfault when shogun_exit() is called before
kernel objects are destroyed)