Revert "Remove preserve-inputs package -- an upgrader removes it from apps"

This wouldn't work well if you run from a Meteor checkout or
without updating your app (via `meteor run --release 0.8.0`)

This reverts commit dc71bd2143ded5b45b94ddcead6a7809544a5eec.
Merge branch 'release-0.8.0' into devel