[core] Fixing squid:S1319 -  Declarations should use Java collection interfaces such as "List" rather than specific implementation classes such as "LinkedList".
(manolama - updated bindings added since the PR)

Signed-off-by: Chris Larsen <clarsen@yahoo-inc.com>

Adding support for memcached binary protocol as described in
https://github.com/memcached/memcached/blob/master/doc/protocol.txt.

Protocol can be set via memcached.protocol property of YCSB memcached workload. if specified
protocol must be "binary" or "text". If unspecified text version is used.

[core accumulo couchbase memcached] Fixing squid:S1155 - Collection.isEmpty() should be used to test for emptiness

The memcached support was extracted from PR #98 by @jbellis, with cleanups to
bring it in line with current APIs and style guide.

This PR also addresses issue #326.