replication: Introduce new APIs to do replication operation

This commit introduces six replication interfaces(for block, network etc).
Firstly we can use replication_(new/remove) to create/destroy replication
instances, then in migration we can use replication_(start/stop/do_checkpoint
/get_error)_all to handle all replication operations. More detail please
refer to replication.h

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Signed-off-by: Wang WeiWei <wangww.fnst@cn.fujitsu.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Message-id: 1469602913-20979-9-git-send-email-xiecl.fnst@cn.fujitsu.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>