Performance improvements

[slothful-vassal]

Hi,

on slower machines with large lists (resulting in large gpx data), there is a big delay when opening a list. The reason is fetchGpx. You can see this effect on your demo instance as well.

I have tried to skip fetching gpx detail when opening a list. Instead, gpx detail is fetched when needed (for the map).

Maybe you like, otherwise it would be nice, if you can make some improvements to reduce the mentioned delay.

Many thanks & regards.

[slothful-vassal]

What have I done in the last few weeks?

• Refactored the map component to improve maintainability.
• Massively reduced the load times of map and list pages by:
  • Using trail bounding boxes to evaluate zoom.
  • Using polyines instead of GPX for lower zoom levels.
  • Using GPX files only for higher zoom levels.

I will update this PR after completing my tests in the next few days.