OEMFile getFrame() ignores CENTER_NAME
When creating reference frame to use with the ephemeris coordinates the `getFrame()` method only uses the value of `REF_FRAME` and ignores the value of `CENTER_NAME`. One of the OEM examples uses `REF_FRAME = EME2000` and `CENTER_NAME = MARS BARYCENTER`. At the same time the OEM standard specifically lists `MCI` as the way to specify the Mars Centered Inertial frame in Annex A.
So it seems we need to change the implementation to translate the center of the reference frame to a new origin based on the `CENTER_NAME` key word. The `CENTER_NAME` can also be another spacecraft, but I don't think we should try to support that.
(from redmine: issue id 334, created on 2017-04-11, closed on 2017-07-27)