Add hook to better handle file refreshes for cached OPIC images

This hook will replace the default cron refresh for Imagecache External that simply refreshes all images after a day. This hook will do the following:

• Checks to see if opic.osu.edu is live and will not attempt a refresh if it is not
• Checks if a file is broken. If it is, it will attempt to refresh immediately
• If image is NOT broken, it will attempt to refresh images that are older than 24 hours within a small window (3AM to 5AM Eastern). This is to avoid a big refresh during peak hours. Refreshes will happen alongside the Imagecache Render custom cron job that runs during this window.

assigned to @canini.16

approved this merge request

merged

mentioned in commit a78f51ae