Save/Restore window positions

- #29 - Settings window
- #28 - zboard
- #27 - turnstile
- turnstile progress
- import keys
- export keys

src/settings.cpp

@@ -122,4 +122,13 @@ QString Settings::getZECUSDDisplayFormat(double bal) {
         return getZECDisplayFormat(bal) % " (" % getUSDFormat(bal) % ")";
     else
         return getZECDisplayFormat(bal);
+}
+
+
+void Settings::saveRestore(QDialog* d) {
+    d->restoreGeometry(QSettings().value(d->objectName() % "geometry").toByteArray());
+
+    QObject::connect(d, &QDialog::finished, [=](auto) {
+        QSettings().setValue(d->objectName() % "geometry", d->saveGeometry());
+    });
 }