SCMTrigger tests for various branch specs

This Pull Request adds integration tests testing the SCM trigger behavior for several branch specs.
As you can read here (https://github.com/jenkinsci/git-client-plugin/pull/135) for some combinations of branch specs in the plugin and branches in the repo CI jobs are triggered again and again without new changes.

Some of the tests depend on the fixes in the git-client plugin (https://github.com/jenkinsci/git-client-plugin/pull/135).
Some other tests are disabled temporarily because the bugs disclosed there are not yet fixed.

This Pull Request also depends on (contains) https://github.com/jenkinsci/git-plugin/pull/230