Automated message deletion

[AFHDubCoLib]

The usage we're considering this for is tracking staff attempts to find missing items. We'd want that data to be cleared when/if an item becomes found, and it'd be great if the plugin could help with that. Best case, we'd be able to tell the plugin to remove all messages from a lost item becomes found. Next best would be a cron that could be set to run daily and delete all messages from items that are not lost. Third best would be a prompt on the checkin screen that alerts the user to the message and provides a button there to delete the messages right from checkin.