Fire ServerListPingEvent for legacy pings.

Currently it is not possible for plugins to modify the MotD or the maximum player count when outdated clients (1.6.4 and older) ping the server from the server list. This will change it so the `ServerListPingEvent` is also called for legacy pings.
- If the MotD contains a second line then it will be removed to prevent strange characters on the client.
- Even though the JavaDoc of `ServerListPingEvent` **clearly states** that [`setServerIcon` will throw an `UnsupportedOperationException` on some implementations](http://jd.bukkit.org/dev/apidocs/org/bukkit/event/server/ServerListPingEvent.html#setServerIcon%28org.bukkit.util.CachedServerIcon%29) I don't think that many developers respect it in their plugins. That's why we should remove the exception for the legacy pings eventually to prevents errors in some plugins. Currently it will just throw an exception if the method is used for legacy pings.