App: Switch to pay-as-you-go licensing

[devemux86]

@lve0200

My other request would be, that we, who have subscribed to the current version would be allowed retaining it, as is. May be you could create a new Kurviger 2.0, where all the future upgrades go, and leave the current version in peace (just stopping new subscriptions, but keeping it there for download as free oder those who have a prof key). Everybody could then decide, staying with the current version, or move on to the new subscription, if the new baby becomes tempting.

Subscriptions seem to be the new model of Locus app.
You can read more details in their announcement:

Locus Map - let's talk future