The goal of this patch is simply to move some classes out of
jenkins_jobs.builder into more appropriately-named modules. This started with
simply moving YamlParser into jenkins_jobs.parser but led to other moves in
order to avoid cyclic imports since YamlParser uses other classes previously
defined in jenkins_jobs.builder.
That said, this patch doesn't intend to address all of the clutter in
jenkins_jobs.builder, mostly just what is necessary to get started working on
YamlParser independent of other classes in that module.
Change-Id: Ie88bf683e495033eb0b670fe29c256a70282735f
4a8b93b8c2