Merkaartor 0.20.0 released

A new version of Merkaartor has been released, the 0.20.0. You can download it in the Download section or on Github Github release 0.20.0.

Short changelog:

• ADD: Implemented OAuth2 authentication.
• ADD: AppImage builds.
• FIX: Fixed CI builds.
• FIX: libproxy and libgps external library handling by build system.
• FIX: CMake unity builds.
• FIX: Windows localization.
• DEL: Removed some dead code, qmake build config.