Admin pipeline support

Pipeline support and enhancements

Jervis is not only a Jar that gets published to Maven central. It is also a Jenkins shared pipeline library.

Recommended plugins

In order to get the full user experience provided by Jervis the following Jenkins plugins are recommended with reasoning.

• Pipeline: Multibranch with defaults plugin. Provides a way to specify a "default" Jenkinsfile for configured multibranch pipelines. This allows you to configure your Jenkins instance to force loading Jervis YAML initially instead of a user's Jenkinsfile. However, Jervis supports loading a user's Jenkinsfile in addition to the Jervis YAML. An example will be discussed further below.
• SCM Filter Jervis YAML plugin. Provides automatic branch filtering from the YAML. Filters are evaluated from the commits which provide the Jervis YAML. If a branch is allowed via YAML branches filtering.

TODO: More admin documentation to come...