Rename Elasti-cache plugin to micro-memcached

[morrowgi]

Elasticache can either be a redis in-memory data store and cache or Memcached memory object caching system. So basically the memcached protocol can be used to seamlessly connect with elasticache. So therefore it makes more sense to rename micro-elasticache to micro-memcached as it should be compatable with both Elasticache cluster or a couchbase cluster with memcached bucket