Add dedicated classes for normalized coordinates and time in CR3BP model

The Circular Restricted Three Body Problem uses normalized coordinates for everything (time, position, velocity, mass attraction coefficient). There are provisions to change between standard PVCoordinates and frames using CR3BPSystem.getRealPV() and CR3BPSystem.getRealAPV() but the same classes are used to hold both the normalized and regular coordinates.

This is confusing. Specialized non-dimensional containers should be used to represent CR3BP coordinates and time to make it clear they are neither AbsoluteDate nor PVCoordinates.

As this would change public APIs, it should wait for version 12.0.