#33 server.network: Expose IoFilterChain

[Hanno Braun]

The network service should enable other classes to access the IoFilterChain. This satisfies several requirements:
* Helper classes must be able to process network messages.
* Helper classes must be able to intercept messages they process, preventing them from being delivered to the game's IoHandler.
* All of this must be completely transparent from the view of the game code.

This task replaces tasks #1830583 and #1830591.

[Hanno Braun]

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This is pretty easy to do and gives some great benefits.
Scheduled for 0.3

[Hanno Braun]

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The same information needs to be exposed on the client side, in order for helper classes to work.

[Hanno Braun]

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Rescheduled for 0.4. I don't want to hold up the 0.3 release any longer.
Increased priority, as this is needed for functionality I want to implement for 0.4 (#1877584).

[Hanno Braun]

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Haven't gotten around to do it in time for 0.4. Rescheduled for 0.5.