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/helper_test.go

@@ -4,6 +4,7 @@
 package eth
 
 import (
+	"crypto/ecdsa"
 	"crypto/rand"
 	"math/big"
 	"sync"
@@ -94,10 +95,9 @@ func (p *testTxPool) GetTransactions() types.Transactions {
 }
 
 // newTestTransaction create a new dummy transaction.
-func newTestTransaction(from *crypto.Key, nonce uint64, datasize int) *types.Transaction {
+func newTestTransaction(from *ecdsa.PrivateKey, nonce uint64, datasize int) *types.Transaction {
 	tx := types.NewTransaction(nonce, common.Address{}, big.NewInt(0), big.NewInt(100000), big.NewInt(0), make([]byte, datasize))
-	tx, _ = tx.SignECDSA(from.PrivateKey)
-
+	tx, _ = tx.SignECDSA(from)
 	return tx
 }