- FeedbackMessage has been subsumed into SystemMessage, which now has three
modes: INFO, FEEDBACK, or ATTENTION.
- Cleaned up methods for sending those system messages.
- on the server: sendInfo(), sendFeedback(), sendAttention()
- on the client: displayInfo(), displayFeedback(), displayAttention().
git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@2635 542714f4-19e9-0310-aa3c-eee0fc999fb1