OF-2730: Change the way channels are closed
As per Alex' suggestion: When closing the channel we switched to using `ctx.channel().close();` rather than calling `close` directly on the context:
`ctx.close()` starts to flow through the `ChannelPipeline` from the point of the `ChannelHandlerContext` while `ctx.channel().close()` will start from the tail of the `ChannelPipeline` all the time.
OF-2731: Update implementation of XEP-0280: Message Carbons
In earlier versions of the XEP, messages eligible for carbon delivery were limited to those of type 'chat'. In later versions, a more broad selection of criteria was added.
This commit updates the criteria for carbon delivery (mostly) to the latest version of the XEP: 1.0.1
