Incorporated feedback from Norman:
- use same pool for boss and worker
- remove ioratio
- disable caching of byte buf allocator
- childoption sendbuf/receivebuf
- fire exception through pipeline

In addition:
- fire failure handler BlockFetchingListener at least once per block.
- enabled a bunch of ignored tests
Added connection pooling.
Removed BlockManager.getLocalShuffleFromDisk.
Fixed test hanging.
Merge branch 'netty-blockTransferService' into sort-benchmark