[KPhotoAlbum] Marble versioning

[Tobias Leupold]

> It just did:
> https://invent.kde.org/education/marble/-/merge_requests/45

But is it correct that they use the KDE Applications version for the 
library? because if so, the versioning can't be used in a meaningful 
manner, as the "major" version increases each year, no matter if they 
changed something or not, and cmake will declare it as incompatible.

I think this is simply not a suitable approach for a library ... the 
version should make us able to detect incompatible API changes, whereas the 
version we have now only allows us to see in which year the release was 
done ... this is simply essentially useless for a library, no?

I mean, they can/should do this for their GUI interface. But not for the 
shared libraries ...

Correct me if I'm wrong of course ;-)