build: Rename the packaging directory

The Linux and Windows packaging recipes don't have any restrictions on
where they have to be located. Snapcraft is the strictest on this.

Moving this to build-aux/ means we can have all the packaging recipes in
one place.

build-aux/linux/fedora/README.elements

@@ -0,0 +1,38 @@
+[fr]
+Collection d'éléments pour QElectroTech.
+
+[en]
+Elements collection for QElectroTech.
+
+[de]
+Bauteilsammlung für QElectroTech.
+
+[es]
+Collección de elementos para QElectroTech.
+
+[pt]
+Colecção de elementos para QElectroTech.
+
+[ru]
+Коллекция элементов для QElectroTech.
+
+[cs]
+Sbírka prvků pro QElectroTech.
+
+[pl]
+Kolekcja elementów QElectroTech.
+
+[el]
+Συλλογή στοιχείων του QElectroTech.
+
+[it]
+Collezione di elementi per QElectroTech.
+
+[nl]
+Elementen collectie voor QElectroTech.
+
+[be]
+Elementen collectie voor QElectroTech.
+
+[da]
+Symbol samling for QElectroTech.