pss: Moved crypto to own package.

Distilled whisper message structure and encryption to default crypto implementation.
Added Topic to PssMsg
Simplified PssMsg Payload to []byte

Author: kortatu

pss/client/client_test.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"github.com/ethersphere/swarm/pss/crypto"
 	"math/rand"
 	"os"
 	"testing"
@@ -48,7 +49,7 @@ type protoCtrl struct {
 var (
 	debugdebugflag = flag.Bool("vv", false, "veryverbose")
 	debugflag      = flag.Bool("v", false, "verbose")
-	cryptoUtils    pss.CryptoUtils
+	cryptoUtils    crypto.CryptoUtils
 	// custom logging
 	psslogmain   log.Logger
 	pssprotocols map[string]*protoCtrl
@@ -76,7 +77,7 @@ func init() {
 	h := log.CallerFileHandler(hf)
 	log.Root().SetHandler(h)
 
-	cryptoUtils = pss.NewCryptoUtils()
+	cryptoUtils = crypto.NewCryptoUtils()
 
 	pssprotocols = make(map[string]*protoCtrl)
 }