[Clean] Cartesian to spherical conversion methods names

In GeoGalaxy class:

• cartesian_to_spherical() -> cartesianToSpherical()
• cartesian_to_spherical2() -> cartesianToSphericalAlternative()

In GeoPoint3D class:

• to_spherical() -> toSpherical()
• to_spherical2() -> toSphericalAlternative()
• to_cartesian() -> toCartesian()