nixos/kubernetes: improvements

- Added option 'cni.configDir' to allow for having CNI config outside of nix-store
  Existing behavior (writing verbatim CNI conf-files to nix-store) is still available.

- Removed unused option 'apiserver.publicAddress' and changed 'apiserver.address' to 'bindAddress'
  This conforms better to k8s docs and removes existing --bind-address hardcoding to 0.0.0.0

- Fixed c/p mistake in apiserver systemd unit description

- Updated 18.09 release notes to reflect changes to existing options
  And fixed some typos from previous PR

- Make docker images for Kubernetes Dashboard and kube-dns configurable

nixos/doc/manual/release-notes/rl-1809.xml

@@ -288,11 +288,24 @@ inherit (pkgs.nixos {
    </listitem>
    <listitem>
     <para>
-     Recommented way to access the Kubernetes Dashboard is with HTTPS (TLS)
+     Recommended way to access the Kubernetes Dashboard is via HTTPS (TLS)
      Therefore; public service port for the dashboard has changed to 443
      (container port 8443) and scheme to https.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     The option <varname>services.kubernetes.apiserver.address</varname>
+     was renamed to <varname>services.kubernetes.apiserver.bindAddress</varname>.
+     Note that the default value has changed from 127.0.0.1 to 0.0.0.0.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The option <varname>services.kubernetes.apiserver.publicAddress</varname>
+     was not used and thus has been removed.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 </section>