accounts, crypto: move keystore to package accounts

The account management API was originally implemented as a thin layer
around crypto.KeyStore, on the grounds that several kinds of key stores
would be implemented later on. It turns out that this won't happen so
KeyStore is a superflous abstraction.

In this commit crypto.KeyStore and everything related to it moves to
package accounts and is unexported.

eth/protocol_test.go

@@ -17,7 +17,6 @@
 package eth
 
 import (
-	"crypto/rand"
 	"fmt"
 	"sync"
 	"testing"
@@ -35,7 +34,7 @@ func init() {
 	// glog.SetV(6)
 }
 
-var testAccount = crypto.NewKey(rand.Reader)
+var testAccount, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 
 // Tests that handshake failures are detected and reported correctly.
 func TestStatusMsgErrors61(t *testing.T) { testStatusMsgErrors(t, 61) }