Add RPC release identifier

Add version recipe which drops the converged release number into
/etc/rcb-release. Will include this recipe in the base role.

Fixes rcbops/chef-cookbooks#772

(cherry picked from commit 722d2e12ce6cbba5a629f8dfd46e5e7905a5ea77)
Merge pull request #163 from claco/add-release-ident

Merged automatically by jenkins after successful build test