Fix SQL type error

[hissy]

Fixes #102, #57, #47

This PR converts values to integers when the table column type is an integer.

You can test this fix by adding an image slider block with entries with no images selected.

[hissy]

@KorvinSzanto

Done.

(BC note: If someone created a custom publisher that uses StandardPublisher as fallback, they must change their code)