Some first steps (don't expect to compile)
Add test script that illustrates the intersection of the ellipse with a circle. This script is for validating the code in cta_irf_elliptical_kern_rho::eval().
Move semiminor and semimajor members to the base class for elliptical spatial models.

Any elliptical model should be defined by semiminor and semimajor axes, these are in fact used in the CTA response computation. Hence they should live in the baseclass, not the derived class.
Implement new variable naming
Add elliptical Npred computation test script and improve elliptical Irf computation test script.
Implement elliptical response computation that is limited to the ellipse region. There still seems to be a problem with the Irf computation as the log-likelihood profiles are not smooth. The Npred computation gives however a smooth profile.
Correct typo in documentation
Correctly copy over all parameters
Improve elliptical Irf and Npred computation.

The binned analysis looks okay, but unbinned shows a strange behaviour for the semiminor axis parameter which results in a strong dependency of Npred on the semiminor axis value. This seems to prevent a nice convergence in unbinned mode.

There is also an open issue to be solved related to the possibility that the minor axis is larger than the major axis. The actual code assumes that minor axis < major axis. If this is not fulfilled, the omega arc computations will be wrong.
Adding an rho integration boundary at rho=semiminor solved the problem with the strange Npred profile.
Put MajorRadius before MinorRadius in the parameter stack.

This appears more natural for an ellipse.
Implement model-based integrations for stacked analysis.

Only the model-based integrations allow a proper and easy handling of the elliptical models.
Set absolute log-likelihood precision to 5e-3.
Add test script for radial response computation
Correctly select rho values
Correct transition point for shell model (was in degrees but the method expected radians; this led to convergence problems with the shell model).
Add test script to illustrate the Psf-based computation for radial models.
Finalize response optimization.
Set default optimizer precision to 5e-3 and limit number of iterations to 100.
Adjust reference fit results to new default optimizer precision of 5e-3.