Change default Progress Deadline to 10m and docs

Merge branch 'f-deployment-improvements' of github.com:hashicorp/nomad into f-deployment-improvements

Deployment watcher gates whether allocs can reschedule

Initial implementation of deployments based on progress 

Never respond with an empty object from the adapter

In production builds only, this will slip into the local store
as a record with no ID, which makes for all sorts of bad news.

Driver health UX improvements

Improved Client handling of failed RPCs

separate drivers by commas

Handle the ErrNoLeader case and apply slower retries. Also when we have
missed the heartbeat retry aggressively, backing off after we have
missed for more than 30 seconds.