Route planning in the demo broken

[mvl22]

The actual planning of a route in the demo has become broken during the 2020 integration work. This needs to be reinstated. It is important to keep it running, not least as this promotes a clear understanding of what should be implemented at the level of the present library.

The library is clearly capable though, as the mobiledev repo client code calls it successfully. It is just the internal demo in this repo that has stopped working.

The "Plan route" link does nothing, and auto-planning does not occur either.

[mvl22]

Some work to reinstate the UI correctness was done in 9ce4ffb, but this is incomplete, as shown in the screenshot below.