Add cesium extras

* python3 -m pip install -e .[cesium]

Signed-off-by: Ryan Friedman <25047695+Ryanf55@users.noreply.github.com>

Author: Ryanf55

setup.py

@@ -97,6 +97,7 @@ def package_files(directory):
                 'MAVProxy.modules.lib.optparse_gui'],
       install_requires=requirements,
       extras_require={
+        'cesium': ['tornado'],
         # restserver module
         'server': ['flask'],
         'recommended': ['flask', 'PyYAML', 'lxml', 'wxpython',