Add usage/description to start_geo.sh

start_geo.sh

 #!/usr/bin/env bash
+# Usage: ./start_geo.sh
+# Description: Restart GeoSphere tile processing. Note this assumes all
+#              containers are currently not running.
 
 echo -ex
 export G2G_PRODUCTS="C01 C02 C03 C04 C05 C06 C07 C08 C09 C10 C11 C12 C13 C14 C15 C16 true_color_night"