Cleanup QML imports and license headers

- Group the imports into Qt, KDE, NeoChat
- Import the latest versions
- Remove unused imports
- Remove unused components
- Unify license header styling

imports/NeoChat/Page/LoadingPage.qml

@@ -1,10 +1,8 @@
-/**
- * SPDX-FileCopyrightText: 2020 Carl Schwan <carl@carlschwan.eu>
- *
- * SPDX-License-Identifier: GPL-2.0-or-later
- */
-import org.kde.kirigami 2.12 as Kirigami
+// SPDX-FileCopyrightText: 2020 Carl Schwan <carl@carlschwan.eu>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
 import QtQuick.Controls 2.12 as QQC2
+import org.kde.kirigami 2.12 as Kirigami
 
 Kirigami.Page {
     title: i18n("Loading")