move continuous integration stack to amethyst jenkins

[Frizi]

Currently the CI checks are done on travis, which unfortunately times out very often on this workload. It needs to be moved to amethyst's jenkins. We already have jenkinsfile ready in this repositry, so I believe it's mostly about setting up the right github integration.

The current jenkins pipeline doesn't test on macOS and iOS devices. We need to figure out how critical it is and either enable macos testing or check if we can get away with not having it right now.