Limit messages sent to clients

**[Original report](https://bitbucket.org/Neptilo/life/issue/16) by Victor Ripplinger (Bitbucket: [Neptilo](https://bitbucket.org/Neptilo), GitHub: [Neptilo](https://github.com/Neptilo)).**

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Messages should only be sent to clients if something has changed.
The frequency at which messages are sent should also be limited.
