+ KerrKS: make it actually work, with the generic integrator. Using the specific integrator is an option, but it is currently broken.
+ The christoffel method may now set a stop condition.
+ myrk4_adaptive does not ignore the stop condition set by myrk4 anymore.
+ Conversions To/From seconds may now be done from/to distances using GYOTO_C as a conversion factor
+ Fix Torus, which was completely broken in Cartesian coordinates.
Include new metric (WIP): NumericalMetricLorene