Add initial Python type casting test
Declare value() method const.
Add automatic type casting in Python interface for GObservation* return values.

Automatic type casting was implemented in the GObservations.i interface using the runtime type casting information that is maintained by the SWIG interface. The function relies on a newly introduced type() method in GObservation that provides as a string the class type.

The former GCTAObservation type casting constructor has been removed as it now should be obsolete.
Add classname() method to all classes and implement full automatic typecasting for the observation Python module.

The classname() method returns in a human readable format the class name. This method is needed for full automatic typecasting in Python. Full automatic typecasting has for the moment been implemented for the observation module.
Remove obsolete typecasts.
Add full dynamic typecasting support to Python modules and remove obsolete typemaps.