Add support for Jenkins' `Folders` plugin

This change allows you to print the full job name when you have
structured your jobs into 'folders' with the 'folders' plugin:

> The Folders plugin allows you to organize jobs in hierarchical folders
> much like how you organize files in directories in your file system.

Too bad that the plugin also modifies the jobname within `cc.xml` in a way that the job names
only show the last folder name which makes the jobnames mostly quite meaningless.

Example:

    Without folders plugin: job-name-build
    With folders plugin: build

See http://jenkins-enterprise.cloudbees.com/docs/user-guide-bundle/folder.html
Improve tests & fixtures