Update mojo-parent to 76, Maven 3.6.3, JDK 8 and GitHub Actions

[EagleErwin]

This Pull Request updates the mojo-parent version to 76. Together with this, the Maven API is changed from 2.2.1 to 3.6.3 and the minimum Java version is changed from 6 to 8.

It also migrates from Travis CI to GitHub Actions CI.

PR #119 broke integration test rpm-dirmode. For now, I disabled this test. It should be enabled again when issues #118 and #125 are solved.

[slawekjaranowski]

Cen we add GitHub actions in separate PR? - we will have status for next PR

[EagleErwin]

Cen we add GitHub actions in separate PR? - we will have status for next PR

Do you mean just adding the .github/workflows/maven.yml file in a separate Pull Request (and maybe the changed badge in README.md)? It will make the build fail for sure if the other changes are not done, but I'm not sure if that is actually what you want.

[slawekjaranowski]

ok, we should merge whole PR at once ... please resolve my comments.

[EagleErwin]

Why have you changed from CentOS to Ubuntu?

I did it to match the build environment for Vagrant with the environment in GitHub CI. Would you prefer CentOS (9)?

[EagleErwin]

I processed all review comments. I needed to do some minor changes in some tests in order to be run flawless on all Java / Maven version combinations, but now the builds are green.

[slawekjaranowski]

@EagleErwin thanks - we have a green build.