Add the function to display the route plan distance in the status bar

[Koine Yuusuke]

Nice to meet you.

I tried adding the function to display the distance of the route in the status bar while using the route-planning function.
If you like, please merge to the source tree.

I am the first to contribute to the foxtrotgps project.
If you don't need this kind of feature addition, or if there is an error in the method of submitting or creating a patch, I would be grateful if you could point me out.
(If there is no problem, I am thinking of adding other suggestions to the route-planning function.)

Finally, thank you for publishing the great software.
Best regards.

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 Koine Yuusuke(koinec) <email address hidden>