Initial Memcached implementation of MapEntityStore CachePool

ASCII protocol without authentication
Memcached implementation of MapEntityStore CachePool

ASCII and BINARY protocols
SASL authentication
Memcached implementation of MapEntityStore CachePool : documentation
Memcached implementation of MapEntityStore CachePool : build

Moved net.spy:spymemcached dependency definition to ~/libraries.gradle
QI-407 Merge branch 'feature/cache-memcache' into develop