Alexander Ziegler / gammalib

…ients argument (#1847)

The eval_gradients() methods duplicate much of the code of the eval() methods. To increase the maintainability of the code, the eval_gradients() methods have been removed, and the computation of partial derivatives is now done by the eval() methods if the optional gradients argument is set to true.

The following new names have been introduced for the spatial model components:
* "PointSource" (alias: "SkyDirFunction")
* "RadialDisk" (alias: "DiskFunction")
* "RadialGaussian" (alias: "GaussFunction")
* "RadialShell" (alias: "ShellFunction")
* "EllipticalDisk"
* "EllipticalGaussian" (alias: "EllipticalGauss")
* "DiffuseIsotropic" (alias: "ConstantValue")
* "DiffuseMap" (alias: "SpatialMap")
* "DiffuseMapCube" (alias: "MapCubeFunction")

… methods from GTools.

Removed size() method.

Renamed filename() method to url().
Renamed fullname() method to operator().

…ilename object. This allows now replacing all std::string filenames by GFilename arguments.

… simplify the code for reading and writing of XML files.

…ll GModelData derivatives

…or 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.

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.

The CTA response was refactored. GCTAResponse was renamed GCTAResponseIrf, and GCTAResponse became an abstract base class for all possible CTA response functions. GCTAResponseIrf derives from GCTAResponse. Also GCTAResponseCube derives from GCTAResponse.

To make this work, the GObservation::response() method now returns a pointer instead of a reference. The interface definition is such that the pointer never can be NULL. The code has been adapted to comply to this new interface.

Upon reading an XML file, GCTAObservation now determines the appropriate reponse type and calls its reader. If no response is specified in the XML file, GCTAResponseIrf will be used by default.

Adapt the code to the usage of GCaldb for response access.