The region replication framework should not be built upon the general replication framework

In this issue we re-implement the 'Async WAL Replication' mechanism fo region replication, to decouple with the general replication framwork. Now, we extend the MVCC write entry to be able to carry an action once it is completed, so we can attach the WAL edits to this action and send them out directly after the write entry is completed, without touch the actual WAL system. So the special 'region_replica_replication' peer is also useless. We also introduce a new replicateToReplica method at region server side for receiving the WAL edits, which has a much simpler logic than the old replay method. After this issue, we do not need to treat META table specially in region replication, as said above, we do not depend on the general replication framework any more. But to avoid effecting the usage too much, the 'config hbase.region.replica.replication.catalog.enabled' is kept, you still need to enable this flag if you want to enable 'Async WAL Replication' support for META table. Rolling upgrading with 'Async WAL Replication enabled is supported. During rolling upgrading, the 'region_replica_replication' will be removed automatically after master is upgraded. And at region server side, if the new replicateToReplica method is not available when it tries to replicate to secondary replicas, it will fallback to use replay method automatically. Please related sections in our ref guide are: http://hbase.apache.org/book.html#async.wal.replication http://hbase.apache.org/book.html#async.wal.replication.meta http://hbase.apache.org/book.html#_async_wal_replication_for_meta_table_as_of_hbase_3_0_0