Achievements

There's now (as of the next reboot) an "achievements" command that lists
various things you have achieved (or, in some cases, not achieved).

There are quite few achievements available so far, but hopefully we'll get
around to adding more.

For old characters the results will look (very) funny. We might get around to
"faking" the data on old characters to fix this.

- Dáin, Achiever-in-Chief