Allow custom settings configs for maven projects

Allow custom settings & global-settings config files to be configured
for maven projects.

In addition, the previously defined empty nodes for these configurations
were misnamed and this corrects that as well.

This change also switches to using an included test as an example.

Change-Id: I9f832f498e358268b3896ead3a78462e408bdd9d
Signed-off-by: Andrew Grimberg <grimbeaj@gmail.com>
Fix "delete-all"

It was broken by 14ed8b12, resulting in:

    $ jenkins-jobs delete-all
    Traceback (most recent call last):
      File "/Users/marca/python/virtualenvs/jenkins-job-builder/bin/jenkins-jobs", line 10, in <module>
        sys.exit(main())
      File "/Users/marca/dev/git-repos/jenkins-job-builder/jenkins_jobs/cmd.py", line 143, in main
        if options.path == sys.stdin:
    AttributeError: 'Namespace' object has no attribute 'path'

Change-Id: I42a3ef9f3cfca7b4667498009351e0027aa316d7
Merge "Fix "delete-all""
Merge "Allow custom settings configs for maven projects"