Move away from TravisCI to Github actions.

https://docs.github.com/en/actions/learn-github-actions/migrating-from-travis-ci-to-github-actions

Tasks:

• Copy current TravisCI builds to actions.
• Build for all platforms instead of Linux only: Linux, Windows and macOS.
• Provide nightly builds for users.
• Build and run Navdatareader to test simulator scenery loading. Compare output databases.