Every message should be identified

[icycrystal4]

At first glance, message should not IDable, just for in most cases, messages will be consumed sequentially in couple of seconds. There is no need to retrieve message randomly by ID, but ID is still useful in some common reasons:

1. locate the duplicated messages
2. issue track.
3. message may be reordered, ID will help us find out why.

[lrita]

Alpha release will support this feature.