tier-1: Add dnf (and for -dev, fetch from copr)

Part of the aim of this project is to make `dnf` "Just work"
in a bootable container native host.

There's some details to work through, but tier-1 is already
large, and this doesn't add much more.

tier-1/dnf.yaml

@@ -0,0 +1,5 @@
+# A full dnf experience at build time, but right now
+# `dnf update` *client side* doesn't do much helpful...
+packages:
+  - dnf
+  - dnf-utils

tier-1/manifest.yaml

@@ -2,6 +2,7 @@
 include:
   - manifest-tier-0.yaml
   - bootable-rpm-ostree.yaml
+  - dnf.yaml
   - firmware.yaml
   - networking-tools.yaml
   - system-configuration.yaml