Moved jclouds-chef to the main repo

Moved jclouds-chef to the main repo. Things to consider:

* Changed parents in pom.xml files to point to the one in the main repo.
* Replaced all `jclouds.version` by `project.version`.
* Added two exclusions to the duplicate finder plugin to avoid conflicts in test-jar resources (core & scriptbuilder).

And also, do not merge this PR until the following is fixed:

* jclouds-karaf IT tests fail because the jclouds-chef feature is not installed. @ccustine could you build this branch and help making the karaf tests pass?
* Once this is merged we should disable the jclouds-chef builds in CloudBees to avoid publishing obsolete snapshots.
* We should also update the read me and contributing files in the jclouds-chef repo to point users to the main one.