Template based job creation

Adds capability of creating new projects for repositories with no job, using an existing Jenkins job as template, either using a single template for all unknown repositories or based on the repository name or group.

Although it doesn't merge automatically, I've cherry-picked the commits producing the conflicts and solved remaining ones, so it is safe to merge manually accepting changes from my branch (using -Xtheirs).

The only test I've not been able to fix is

    spec/values/project_spec.rb:113 # GitlabWebHook::Project when determining if matches repository url and branch when parametrized does not match when branch parameter is not of supported type

which produces a "only string parameters for branch parameter are supported" warning instead of the expected exception.
The is_template is there basically because on "traditional" auto-creation, the branch for the new job must be the one on payload, where or templates the branch configured on the template should be kept.
Or better, checked for match against payload before proceeding, which I've just realized. I'll attempt that on near future