Merged requested to merge louis_aucouturier/orekit:Issue-666 into develop
- Definition of the AbstractHatchFilter, Doppler, Carrier Phase (Single Frequency and Divergence Free) Hatch filters, and the associated PseudoRange smoother classes. An ObservationDataSetUpdate has been included to allow the filtered data to be carried along with the original data.
- Definition of the tests.
- The Carrier Phase filters were tested against cases presented in the gLAB tutorial. The necessary commands and data have been included.
Fixes #666 (closed)