ADD: new track message, Entity class and Position class

libs/geographiclib/README.md

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+# GeographicLib
+
+GeographicLib is a small C++ library for
+
+* geodesic and rhumb line calculations;
+* conversions between geographic, UTM, UPS, MGRS, geocentric, and local
+  cartesian coordinates;
+* gravity (e.g., EGM2008) and geomagnetic field (e.g., WMM2020)
+  calculations.
+
+It is licensed under the MIT License; see
+[LICENSE.txt](https://geographiclib.sourceforge.io/LICENSE.txt).
+
+## Links:
+
+* Library documentation: https://geographiclib.sourceforge.io/C++/doc
+* Change log: https://geographiclib.sourceforge.io/C++/doc/changes.html
+* Git repository: https://github.com/geographiclib/geographiclib
+  * Releases are on the [`release`](../../release) branch, and specific
+    releases are tagged as, e.g., [`r1.52`](../../tree/r1.52),
+    [`r2.0`](../../tree/r2.0), etc.  This is the appropriate branch
+    for most *users* of GeographicLib.
+  * The main branch is [`main`](../..) and most development is done on
+    the [`devel`](../../tree/devel) branch.  These branches are for the
+    *developers* of GeographicLib.  Tags [`v1.52`](../../tree/v1.52),
+    [`v2.0`](../../tree/v2.0), etc., are aligned with the
+    corresponding release tags `r1.52`, `r2.0`, etc.
+* Source distribution:
+  https://sourceforge.net/projects/geographiclib/files/distrib-C++
+* GeographicLib: https://geographiclib.sourceforge.io
+* GeographicLib in various languages:
+  https://geographiclib.sourceforge.io/doc/library.html#languages
+* Author: Charles Karney, <charles@karney.com>