This commit sees JJBConfig start to take the form it ought to have,
namely using attributes to represent different logical sections of
configuration that target specific subsystems of JJB.
It also moves ConfigParser data retrieval from
jenkins_jobs.modules.helpers.get_value_from_yaml_or_config_file() to
jenkins_jobs.config.JJBConfig.get_module_config()
TODO: Add JJBConfig tests to validate the behavior of JJBConfig in
specific circumstances.
Change-Id: I053d165559f5325a2f40b239117a86e6d0f3ef37
4f04de1f9a