V2.0.0

Code changes:
major overhaul, moving from SQLite backend to a rust based one, and rearchitecturing from multithreaded message passing to entirely synchronous method calls (unfortunately a little bit spaghetti). This gives no feature improvement for the native version, but we can now compile to wasm!

User facing changes:

• the new backend is faster! No more waiting to see all your different selections popping into existence on the map one by one.
• The app will be available on gmap.turun.de!!!