Clarify information in Debezium connector for SQL Server doc

Hi,

This might get borderline nitpicking, but I believe the SQL Server connector docs may benefit from a little improvement here and there.

Please keep in mind that the points that follow are from a developer standpoint - some concepts might be opaque to readers not really used to DB administration, so a little hand-holding would go a long way.

1. v1.3 should be stable, I believe?

2. Which table is which here?

The CDC table, or the "source" table, so to speak?

As far as I can tell from the connector logs (convoluted scenario: Debezium within Kubernetes managed by strimzi.io) it's a SELECT * from the "source" table. There might be no LSN in the CDC tables, I've been told by our DBA that the CDC tables do have an expiration of sorts. Or what if no changes have been recorded yet (very old lookup tables)? Which table is it again?  

I can find out by testing (and we did), but I'd really love to be sure that the "initial snapshot" (done once) is sending all the rows in the tables subject to CDC via read events and then it'll start streaming the actual change events.

I might be of course misreading it, but I'd be more comfortable with a different wording.

3. Timestamp

Here it says that ts_ms is the processing time, then it says that, by default, is the database operation timestamp (which is indeed what we need).

Thank you for your time and your valuable contribution to the community.