Move QML files to src/qml and don't use internal qml modules

src/qml/Page/LoadingPage.qml

@@ -0,0 +1,13 @@
+// SPDX-FileCopyrightText: 2020 Carl Schwan <carl@carlschwan.eu>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+import QtQuick.Layouts 1.15
+import QtQuick.Controls 2.12 as QQC2
+import org.kde.kirigami 2.19 as Kirigami
+
+Kirigami.Page {
+    Kirigami.LoadingPlaceholder {
+        id: loadingIndicator
+        anchors.centerIn: parent
+    }
+}