Basic support for cache store

including minimum support for memcached using net.spy:spymemcached:2.11.4

Signed-off-by: Robin Smith <robin.smith@clicktravel.com>
FileStore has FileItems, DatabaseTemplate has Items so an ItemCache can have "items" also.

Object seems too low-level even though at the Java-level they are still Objects (so are Exceptions and HttpClient etc.)