Respect question enabled on Evaluations

Evaluations now only show visible questions, but the reports will continue to show all responses including questions that have been disabled.

This is to allow evaluations to change over time, without deleting prior responses we need for reports, or requiring users to re-do their evals when the whole evaluation is replaced.

Requires https://github.com/silverorange/inquisition/pull/4
Missing `count()`