Fix offline leaflet

[george-gca]

Fixes #2419 by downloading leaflet images. Also changed the path where the libraries are downloaded to avoid not downloading files with same name.

[CheariX]

I'm wondering how the images can downloaded beforehand?
I assume that only the initial images are downloaded but when you scroll the map, there will be missing images?

[gockar]

I'm wondering how the images can downloaded beforehand? I assume that only the initial images are downloaded but when you scroll the map, there will be missing images?

Sorry for the confusion, I was referring to the static graphics for markers etc. that are delivered together (or not...) with the JS and CSS. Downloading all the maps could quickly become a lot. The source can be selected individually and they are downloaded dynamically.

[george-gca]

Yes, there is so much we can do about offline support. Check if it is working now @gockar.

[gockar]

Sorry, wanted to point out that all the maps themselves should not be downloaded as they consume an extreme amount of memory. My problems are solved with the changes, thank you!