Adding user data to SpacecraftState
All propagators provides a way to propagate additional state. The
can register AdditionalStateProviders instances representing already integrated states,
and integrated propagators (numerical and DSST) can register AdditionalEquations representin
differential equations for these states. In both cases, the output is difficult to retrieve
and lives aparts from the SpacecraftState.
Having these data available within the SpacecraftState would be much simpler.
A way to add user data may also prove useful outside of propagation.
(from redmine: issue id 132, created on 2013-04-08, closed on 2013-04-08)