Remote Read Acceleration with JXIO

Add support to remote reads with RDMA over JXIO library.
Remote reads can be done using TCP client with NIO or NETTY servers, or RDMA client and server.
Each mode can be configured and changed easily using new pluginability feature.

By default RDMA code is not compiled, to use it user must install JXIO and build Tachyon with -Pjxio flag
i moved the class outside of the nio package beacuse rdma uses it as well
the function has to be public to be visible from the nio and rdma packages