Revert "Add "Activity Summary" reports"

This reverts commit 8dcedb8537b38191e7fa8a9d260ace82240d4f7b.
Prevent dev mode reset from running if not in dev mode

Otherwise, anybody who can find the URL can run the reset.
Skip generating stats for site course

We're not interested, and there's nothing to see anyway other than accesses.
Remove student access to reports

We don't want students to see the raw reports, as some may attempt
to game the system if they can see what the teachers see.
Remove closing PHP tag from version.php
Use correct string for "Resources: Resource details on students" report title
Update help for Gismo 3 (including new screenshots)