Fixes #856

The test shows that using thwo proapgators work, but embedding them in a
propagator parallelizer does'nt work.

Fixes #862

The switch to new API is not complete yet, we still use instances of
AbstractJacobian, we just declare them as MatricesHarvesters.

Fixes #847

JacobianColumnGenerator does not work yet. There is a scheduling
problem with StateTransitionMatrixGenerator because Hipparchus does not
have any ordering feature. AbstractIntegratedPropagator should probably
merge all objects registered using addIntegrableGenerator into one
single SecondaryODE presented to Hipparchus to work around this problem.

These containers are intended as replacements for HashMap when the
number of keys is very small (such as in spacecraft states).

They have smaller overhead, are more debugger-friendly (when dealing
with additional states and derivatives), and all in-place
incrementation.

The new interfaces StackableAdder and IntegrableAdder allow to build
state incrementally according to some dependency order if some adders
require additional states or derivatives computed by other adders.

Fixes #851

Fixes #850