Load layers on action

[maze2point0]

Rebased ors_graph into this branch.

In my opinion ready to be merged.

We will:

• use the ors_graph now for routing
• not be able to visualize brightness and safety due to the large size and therfore long loading times. This will be adressed in another branch

[maze2point0]

For visualizing I am looking into using vector tiles in a shiny leaflet setting. Here are some ressoruces I have found so far:

hosting a local server for mbtiles and consuming in a deck.gl client. 900MB of data are quickly visualized.
https://www.milesmcbain.com/posts/vector-tiles/

consume pm tiles in R leaflet via leafem package
https://r-spatial.github.io/leafem/reference/addLocalFile.html?q=vector#null

code to consume local mbtiles / pbf's in leaflet via registerPlugin
r-spatial/leafem#34