* qp: fetch_source_query: store card-id for each query

we want to be able to determine further in the pipeline
whether a query came from a card (i.e. saved question)
or not

* qp: annotate: remove join-alias if source is a card

If the source is a card, the front-end should be able to treat it
similar to a database view so we should not expose the join
aliases outside.

If the card is on the right side of the join though, the alias
should still exists and refers to the current-level join alias.