Initial Netty implementation for networking

Split into 1 LoginServer and 1 ChannelServer per channel.

There is still a lot of cleanup and refactoring to be done.
Currently, the reliance on IoSession holding client state
is the most pressing issue to be addressed.

src/main/resources/log4j2.xml

@@ -26,5 +26,6 @@
         </Root>
         <Logger name="org.apache.mina" level="info"/>
         <Logger name="com.zaxxer.hikari" level="info"/>
+        <Logger name="io.netty" level="info"/>
     </Loggers>
 </Configuration>