This support is in addition to the legacy support for IERS
UTC-TAI.history file which is still supported and also enabled by
default.

Thanks to Lucian Barbulescu for providing the translation.

The Eckstein-Hechler propagator now generated Cartesian orbits, with
velocity computed to be fully consistent with model evolution. A side
effect is that if users rebuild circular parameters from the generated
orbits, they will generally not math exactly the input circular
parameters (but position will match exactly).

Fixes issue #180.

Bulletin A provides rapid service and prediction, whereas bulletin B
provides final values. Bulletin A are suitable for real-time operation
and bulleting B more oriented towards a posteriori accurate analysis.

Thanks to Ioanna Stypsanelli!

This was the last par still in apt format. Now everything uses markdown.