Adding possibility to use a different cache-backend for locking and caching

- Renaming *LockDriver to *Lock since it isn't a "driver" anymore

src/Core/Cache/MemcacheCache.php

@@ -148,4 +148,9 @@ class MemcacheCache extends AbstractCache implements IMemoryCache
 		$cachekey = $this->getCacheKey($key);
 		return $this->memcache->add($cachekey, serialize($value), MEMCACHE_COMPRESSED, $ttl);
 	}
+
+	public function __toString()
+	{
+		return self::TYPE_MEMCACHE;
+	}
 }