[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.
When I ask intellij what references this class, I get the following list:

```
RemoteBlockInStream
TachyonFile
DataServerTest
DataServerMessage
NIODataServer
```

Netty code doesn't use this class.

Also, rather keep this in the same packet since when I didn't, there were scope issues and tests were failing.  

Can I address these concerns when I am doing the remote write patch?  I need to redo the way the client generates messages and I will need to update NIO for any changes to the read path.