This is the first step in removing the config dependency on "project".
This change is backwards-compatible because the value for this new
attribute defaults to the value from the provider.
Common metadata state is now stored
Optimistic locking support added to common_metadata
Revisions to keys in project metadata are now reflected in the project state
Wrote tests for project metadata (all pass)
Relaxed test conditions to work on projects with extra keys
Added documentation for project metadata
Seth Vargo