Issue #2820 - Disable similar colors

Pull request that fixes #2820.

Some tests:
![capture1](https://cloud.githubusercontent.com/assets/783393/3897365/faa144de-2260-11e4-95c9-06b25e9643e6.PNG)![capture2](https://cloud.githubusercontent.com/assets/783393/3897363/fa9af99e-2260-11e4-8861-fad44a134c81.PNG)
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![capture3](https://cloud.githubusercontent.com/assets/783393/3897364/fa9ce0c4-2260-11e4-8df3-36432417df6e.PNG)![capture4](https://cloud.githubusercontent.com/assets/783393/3897366/faa1aaaa-2260-11e4-8644-9bbfc02812c3.PNG)
All these color-related methods should be moved into LobbyCommands or their own server trait.  The server class should be limited to a minimal set of networking-related logic.  You can validate colors on player join by implementing the `IClientJoined` interface on the server trait that handles the color validation.