Migration of the dsst standalone to C/C++

The Draper Semi-analytical Satellite Theory (DSST) Standalone orbit propagator combines the speed of analytical propagators with the accuracy of numerical propagators. The DSST exhibits linear behavior, ease of estimation, and accurate measure of orbital uncertainty over extended periods of time. DSST is publicly available in its original Fortran 77 form and in the Orekit Java library. The current project migrates the original Fortran 77 DSST code to C/C++. The original design will be maintained as much as possible in the initial version of C/C++ DSST, to facilitate use of existing test resources.