hadoop: remove hadoop shim

The in-tree Hadoop shim was a combination of libcephfs wrapper, and the
bits to support Hadoop. This has been replaced by src/java that
implements generic libcephfs wrappers, and externally, the hadoop shim
(see docs).

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Merge pull request #597 from ceph/remove-hadoop-shim

This branch built fine on the gitbuilders and the list of removed files looks good to me.

Reviewed-by: Greg Farnum <greg@inktank.com>