* Allow returning list information and other data in 404s.
On read it'll output data and/or warnings on a 404 if they exist. On
list, the same behavior; the actual 'vault list' command doesn't change
behavior though in terms of output unless there are no actual keys (so
it doesn't just magically show other data).
This corrects some assumptions in response_util and wrapping.go; it also
corrects a few places in the latter where it could leak a (useless)
token in some error cases.
* Use same 404 logic in delete/put too
* Add the same secret parsing logic to the KV request functions
* plugins/gRPC: fix issues with reserved keywords in response data
* Add the path raw file for mock plugin
* Fix panic when special paths is nil
* Add tests for Listing and raw requests from plugins
* Add json.Number case when decoding the status
* Bump the version required for gRPC defaults
* Fix test for gRPC version check
