* Add explanation to help text and flag usage text
* KV get with new mount flag
* Clearer naming
* KV Put, Patch, Metadata Get + corresponding tests
* KV Delete, Destroy, Rollback, Undelete, MetadataDelete, MetadataPatch, MetadataPut
* Update KV-v2 docs to use mount flag syntax
* Add changelog
* Run make fmt
* Clarify deprecation message in help string
* Address style comments
* Add `kv rollback`
Like `kv patch` this is more of a helper than anything else; it provides
a single command to fetch the current version (for CAS), read the
version you want to roll back to, and set it as the new version (using
CAS for safety).
Chris Capurso