not clear which ways are not covered

[joshinils]

In comparison to wandrer.earth, i do not know which ways will get painted in blue on the map after i upload a sequence taken there.
On wandrer.earth I can enable untravelled ways on my Big Map (login required), I would like this for KartaView aswell.

[miruna-craciun]

Closing this as a duplicate for #327 - will follow up there w updates.