Checkout projects into project-id/project_name subdirector

I had a situation where in some cases a project had dependencies on others projects being in the same directory. This change corresponds with changes in gitlab-ci pull request https://github.com/gitlabhq/gitlab-ci/pull/301 which exposes the project name. With this the runner can checkout the main project into a subdirectory based on the project name and then the build script can handle checking out the project dependencies for building.