Add logs about usage / delete inactive redirects

Issue Summary

I think it'd be good to have a log on how often each redirect is used.

Ideally, I'd like to have a count of how many hits each redirect has received within a specified time period. The time period is determined by a setting. Alternatively, it could be logged when the redirect received the last hit. The number itself might not be that important.

Reason: It'd be nice to get rid of redirects once they aren't being used anymore. For example, if no one visited the redirected page for half a year, it's relatively safe to get rid of the redirect.

Taking it a step further, you could also imagine having an automatic cleanup. You could then specify that redirects are automatically deleted as soon as they have been inactive for a specified time period. For example, every redirect that hasn't been used for half a year would be removed.