Add GObservations::logL() method and add const attribute to GOptimizerFunction::value() method.
Add rampdown to Psf access operator at the edge of the Psf so that no steps occur in the log-likelihood function.
Add offset subtraction to provide smooth Psf edges.
Add missing methods to Python interface
Use a sqrt delta binning and add a central cap.
No need anymore to add 10% margin to delta range.
Avoid unnecessary computations.
Correct indentation
The romb() method now returns a result even if it is inaccurate.

Before, 0 was returned in case of inaccurate results. This is bad. We want some result, even if it's not accurate.
Add smooth_robust() method to compute smooth noise-robust derivatives.
Some code changes in the course of the Irf integration investigation.