Needs to be more like http.

There was a bug in jobspec parsing, a bug in CheckRestart merging, and a
bug in CheckRestart canonicalization. All are now tested.

Fixes #3380

Adds address_mode to checks (but no auto) and allows services and checks
to set literal port numbers when using address_mode=driver.

This allows SDNs, overlays, etc to advertise internal and host addresses
as well as do checks against either.

add conversion for KillSignal for api/struct representation of task

Fixes #2441

Defaults to 0 (no delay) for backward compat and because this feature
should be opt-in.

This PR allows a template to specify the Vault grace duration.

Fixes https://github.com/hashicorp/nomad/issues/2922

Fixes #2678

This PR fixes our vet script and fixes all the missed vet changes.

It also fixes pointers being printed in `nomad stop <job>` and `nomad
node-status <node>`.

This PR removes defaulting from the parse, fixes some regressions that
existed as part of the parser refactor and fixes the tests.

This PR allows setting the file permissions of the rendered template.