ClusterManager: Implements support of remote clusters.

After this change users will be able to:
* Create cluster and add/remove servers to it
* Install apps on remote cluster
* Move already installed apps between clusters
* Apps running on server being removed will auto-migrate
  to another server from that same cluster

This is achieved by:
* Installing and running minimal version of dodo on remote cluster
* Ingress-nginx is installed automatically on new clusters
* Next to nginx we run VPN client in the same pod, so that
  default cluster can establish secure communication with it
* Multiple reverse proxies are configured to get to the
  remote cluster service from ingress installed on default cluster.

Next steps:
* Support remote clusters in dodo apps (prototype ready)
* Clean up old cluster when moving app to the new one. Currently
  old cluster keeps running app pods even though no ingress can
  reach it anymore.

Change-Id: Iffc908c93416d4126a8e1c2832eae7b659cb8044
diff --git a/core/installer/welcome/appmanager-tmpl/all-clusters.html b/core/installer/welcome/appmanager-tmpl/all-clusters.html
new file mode 100644
index 0000000..843381f
--- /dev/null
+++ b/core/installer/welcome/appmanager-tmpl/all-clusters.html
@@ -0,0 +1,21 @@
+{{ define "header" }}
+<h1>Clusters</h1>
+{{ end }}
+
+{{ define "content"}}
+<form action="/clusters" method="POST">
+	<fieldset class="grid">
+		<input type="text" name="name" placeholder="name" />
+		<button type="submit" name="create-cluster">create cluster</button>
+	</fieldset>
+</form>
+<aside>
+	<nav>
+		<ul>
+			{{ range .Clusters }}
+			<li><a href="/clusters/{{ .Name }}">{{ .Name }}</a></li>
+			{{ end }}
+		</ul>
+	</nav>
+</aside>
+{{ end }}