new error codes for invitations feedback.
batch invitations didn't actually get used anywhere.
whitelist/blacklist error feedback for invitations
trivial comment added.
concert error code for disrupted connections.
Merge branch 'hydro-devel' of https://github.com/robotics-in-concert/rocon_msgs into hydro-devel
Merge pull request #42 from jack-oquin/hydro-devel

API updates for #41