Riak 1.4 Feature: Protocol Buffers Bucket Properties

Riak 1.4 adds all known, standard bucket properties to the Protocol
Buffers transport for setting and getting, and adds the "reset" or
"clear" feature as well.

- [x] Support all bucket properties over PB
- [x] Support "reset" or "clear" request/response over PB
- [x] Feature detect whether the server supports 1.4 bucket props over PB