Implement hover tools for precland graphs

[dayjaby]

https://docs.bokeh.org/en/latest/docs/user_guide/tools.html#hovertool

With the hover tools (or by any other means) it should be possible to derive valuable information from the graphs, e.g.:

• how accurate is the precision landing detection depending on the altitude of the drone

[matthewgan]

Maybe it can be integrated with JyputerNotebook within Flight Review