Add TiDB DM

[dveeden]

Please add support for DM

[dveeden]

cc @csuzhangxc @tisonkun

[csuzhangxc]

cc @lance6716

[lance6716]

DM will store dump files and relay logs in local disk. If we mount same accessible directory to multiple docker images, maybe we could imitate shared local states by DM-worker.
cc @GMHDBJD

[GMHDBJD]

DM will store dump files and relay logs in local disk. If we mount same accessible directory to multiple docker images, maybe we could imitate shared local states by DM-worker.
cc @GMHDBJD

LGTM