Jael now stores a `step` that is combined with the original salt to
produce a new code. A `%step` card is used to increment that value,
and effectively resetting the keys. Because the first `step` is zero,
the first code is the same as before.
Eyre was changed to be notified with `%code-changed` so it can forget
old cookies, sessions and discard all the existing channels.
A new generator was added |code, that does both querying and
resetting the code
|code :: shows current code, step and help
|code %reset :: changes the code
The old +code generator still works correctly.
