Recent authors

Added an endpoint that allows you to check whether an OAE user has made
a change to a pad in the last 15 minutes. Edits are tracked per pad/user
and are periodically cleaned.
No they don't. In fact, if they somehow fail to read the `APIKEY.txt` file .. [they generate one..](https://github.com/ether/etherpad-lite/blob/develop/src/node/handler/APIHandler.js#L28)