It would be nice to have ncmonitor parse through all existing ncredir entries and verify that the redirection endpoints still exist/serve pages. We could invoke a send_email() with a list of any domains that are failing.

• We'd might want to verify modules/mediawiki/files/apache/sites/redirects/redirects.dat as well as the usual redirection datfile, something ncmonitor hadn't touched before. Same repo, which makes it easier.
• Would this run as part of the main program execution or in a separate argument, such as --verify-redirections? Further question: Maybe the other main functions could/should be split off to their own flags for more granular execution as well?