Feature: Add command to copy overlay and run extensions

[techmunk]

I'm currently managing some arkdep installs with ansible. As I update and make changes to files under /overlay, it would be nice to have a single command to "sync" the overlay with the current deployment, and possibly/optionally run the extensions

Via ansible I currently unlock rootfs, copy overlay to / and then relock and run extensions. This works fine, but it would be nice to encapsulate this in an arkdep provided command