gui: rename encrypt(), blank(), and askPasshprase()

as well as disablePrivateKeys() to be consistent in naming.

src/qt/walletcontroller.h

@@ -118,7 +118,7 @@ Q_SIGNALS:
     void created(WalletModel* wallet_model);
 
 private:
-    void askPasshprase();
+    void askPassphrase();
     void createWallet();
     void finish();