To streamline file installation, use an associative array to declare
targets, source file, mode, user and group owner.

Be verbose about the installation of files.

Add usr/share/factory/etc/profile.d/locale.sh, so that etc/ profile.d/
locale.sh can be replaced by a factory file in case /etc is deleted.
Extend tmpfiles.d setup for etc/profile.d/locale.sh.

Add /etc/arch-release as file (also to factory), as it is seemingly
still used by legacy OS detection methods (looking at you cmake).

Signed-off-by: David Runge <dvzrv@archlinux.org>