Default values of xtypes in expert plot

[BraveFalcon]

Code for expert_plot from documentation is not working. Error message: "ERROR:root:Invalid x_type argument None". One need to manually specify elevation_profile_x_type and pace_graph_x_type. I think it will be more user friendly to set "distance" as default value.

[FABallemand]

Thank you for reporting this issue.
I will try to fix and improve the plot functions in the coming weeks.