Associate every deposit with the static address parameters that created
it. This lets restored deposits recover the correct script and signing
keys instead of assuming the legacy root address.
The Parameters struct describes the keys, expiry and pkScript that
define the static address script, so its natural home is the script
package. Moving it there lets staticutil drop its dependency on the
address package and lets callers reuse a single type alongside
script.StaticAddress and script.NewStaticAddress.
No behavior change.
Closes#1056
