This PR exposes the following existing`consul-template` configuration options to Nomad jobspec authors in the `{job.group.task.template}` stanza.

- `wait`

It also exposes the following`consul-template` configuration to Nomad operators in the `{client.template}` stanza.

- `max_stale`
- `block_query_wait`
- `consul_retry`
- `vault_retry` 
- `wait` 

Finally, it adds the following new Nomad-specific configuration to the `{client.template}` stanza that allows Operators to set bounds on what `jobspec` authors configure.

- `wait_bounds`
Co-authored-by: Tim Gross <tgross@hashicorp.com>
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>