public Builder setVirtualGatewayFactory(VirtualGatewayFactory gatewayFactory) {
            mConfig.gatewayFactory = gatewayFactory;
            return this;
        }
Set the factory of gateway, the gateway will handle some intercepted actions before the
server and client received the final data.

@param gatewayFactory A factory of gateway.
@return this {@link Builder} object to facilitate chaining method calls.
netbare-core/src/main/java/com/github/megatronking/netbare/NetBareConfig.java