Lava Streams

[gabrielhase]

Implement drawing of lava streams in a separate SVG layer. The lava streams don't follow the actual path but a simplified path in the directions north, west, south, and east (maybe even 8 steps) and the distance in kilometers.

• Gather the necessary data for the lava streams from the printed map.
• Draw lava streams according to the direction and length.
• Instead of drawing lava streams on top of each other when more than one lava stream reached a certain location, draw the lava streams as broader bars.
• Tooltips indicating the years the lava streams reached a certain location.

=> This is quite involved and thus a nice to have feature. It should be implemented only at the very end.