add option to tag DDB table(s) created

Many organisations have a "no untagged" resource policy; s3guard runs into this when a table is created untagged. If there's a strict "delete untagged resources" policy, the tables will go without warning.

Proposed: we add an option which can be used to declare the tags for a table when created, use it in creation. No need to worry about updating/viewing tags, as the AWS console can do that