* cli: add -json flag to support job commands
While the CLI has always supported running JSON jobs, its support has
been via HCLv2's JSON parsing. I have no idea what format it expects the
job to be in, but it's absolutely not in the same format as the API
expects.
So I ignored that and added a new -json flag to explicitly support *API*
style JSON jobspecs.
The jobspecs can even have the wrapping {"Job": {...}} envelope or not!
* docs: fix example for `nomad job validate`
We haven't been able to validate inside driver config stanzas ever since
the move to task driver plugins. 😭
