[TACHYON-62] Netty

Netty implementation of the data server.

This patch is not done yet.  Its intent is to show the work I have right now for commenting.

This PR should not be merged until performance results come in.
Sorry that i am reviewing NIO based DataServer code too. Need try/catch/finally here as mSelector#close never be called if mServerChannel.close() throws IOException. If you think this issue is not related to this PR then we can file a JIRA. Thanks