Move UtilitiesPage and media_keys into separate folder

The QML at the moment is a giant mess. Moving pages into individual
folders and properly abstracting the sub components of the pages will
allow for much easier development and better error messages.
Additionally it will prevent polluting the global namespace. Really, all
the reasons for avoiding globally available values and using
abstractions in regular programming also come into play here.

src/res/qml/RootPage.qml

@@ -3,6 +3,7 @@ import QtQuick.Controls 2.0
 import QtQuick.Layouts 1.3
 import matzman666.advsettings 1.0
 import "." // QTBUG-34418, singletons require explicit import to load qmldir file
+import "utilities_page"
 
 MyStackViewPage {
     id: rootPage