Added collision package

Collision package

Added the collision package which contains the CollisionDefinition class as well as multiple methods to compute the probability of collision between two collision object.

Probability of collision

The following probability of collision computing methods were added :

1. Foster1992 (recommended method)
2. Alfriend1999 (maximum probability of collision method)
3. AlfriendMax1999 (maximum probability of collision method)
4. Chan2008
5. Alfano2005
6. Serra2015 (recommended method)

In addition, the CollisionDefinition class completely defines the collision between two given collision object. Its main outputs are :

• Mahalanobis distance.
• Diagonalized combined covariance in the collision plane.
• The projected position of the secondary collision object onto the rotated collision plane (primary collision object at the origin).

FrameTools

Added the FrameTools class in the frames package in order to convert to other frame from/to CCSDS Frame facade or Orekit Frame.

ExtremumApproachDetector

Added the ExtremumApproachDetector, in the propagation.events package, which detects farthest and closest approach with another given PVCoordinates provider.

Other (Independent from the collision package)

IntegratorBuilder

Added the possibility to create an ODEIntegratorBuilder from an AbsolutPVCoordinates by using the already existing NumericalPropagator.tolerances(double dP, AbsolutePVCoordinates absPva) method.