Support for a custom command to flush Redis database.

[eltherion]

Hi, I'm evaluating ScalaCache usage, but I've got one problem. In order to avoid accidental flushing of a Redis prod database we have this configuration enabled (example aliases, ofc):

rename-command FLUSHALL FLUSHALLNEW
rename-command FLUSHDB FLUSHDBNEW

That means standard:

removeAll[T]()

will not work, bc it uses hardcoded FLUSHDB command resulting in that exception:

  redis.clients.jedis.exceptions.JedisDataException: ERR unknown command `FLUSHDB`,
  with args beginning with: 
  redis.clients.jedis.Protocol.processError(Protocol.java:130)
  redis.clients.jedis.Protocol.process(Protocol.java:164)
  redis.clients.jedis.Protocol.read(Protocol.java:218)
  redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:341)
  redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:240)
  redis.clients.jedis.BinaryJedis.flushDB(BinaryJedis.java:361)
  scalacache.redis.RedisCache.$anonfun$doRemoveAll$1(RedisCache.scala:20)
  scalacache.AsyncForId$.delay(Async.scala:48)
  scalacache.redis.RedisCache.doRemoveAll(RedisCache.scala:17)
  scalacache.AbstractCache.removeAll(AbstractCache.scala:76)
  scalacache.AbstractCache.removeAll$(AbstractCache.scala:75)
  scalacache.redis.RedisCache.removeAll(RedisCache.scala:12)
  scalacache.package$RemoveAll.apply(package.scala:63)

Is there any workaround for that? I don't want to mix libraries and I would like to avoid low level calls, but I might accept it if inevitable.