protobuf message type for dht messages

dht.proto

package dht;

//run `protoc --go_out=. *.proto` to generate

message DHTMessage {
	enum MessageType {
		PUT_VALUE = 0;
		GET_VALUE = 1;
		PING = 2;
		FIND_NODE = 3;
	}

	required MessageType type = 1;
	optional string key = 2;
	optional bytes value = 3;
}

We'll need more message types ( to do the Sloppy part (Coral), Provide/FindProviders in routing/routing.go )

e.g.

message DHTMessage {
  enum MessageType {
    PUT_VALUE = 0;
    GET_VALUE = 1;
    ADD_PROVIDER = 2;
    GET_PROVIDERS = 3;
    FIND_NODE = 4;
    PING = 5;
  }

  required MessageType type = 1;
  optional string key = 2;
  optional bytes value = 3;
}

or something. The PROVIDER stuff is the sloppy put/get, meaning, instead of storing ONE value in the entire DHT, we store a set of values, or rather, a set of peers who can return the value. (if interested, see coral, dhash, mainlineDHT for why this is a good idea). and each item in the set gets put/expires independently. (avoids multiple-writer races, which would be bad if you had to GET -> modify -> PUT the set as a regular, single value)

(we implement both regular PUT/GET and the PROVIDER PUT/GET because some values are small enough to store in the DHT itself (i.e. IPNS mappings) while others are too large (regular objects)

Ive updated my type to reflect this and will be pushing it soon.