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/task.html b/core/installer/welcome/appmanager-tmpl/task.html
new file mode 100644
index 0000000..699a660
--- /dev/null
+++ b/core/installer/welcome/appmanager-tmpl/task.html
@@ -0,0 +1,30 @@
+{{ define "content"}}
+Installation in progress (feel free to navigate away from this page):
+<ul class="progress">
+    {{ template "task" .Task.Subtasks }}
+</ul>
+
+<script>
+ async function refresh() {
+	 try {
+		 const resp = await fetch(window.location.href);
+		 console.log(window.location.href, resp);
+		 if (resp.ok) {
+			 if (window.location.href != resp.url) {
+				 location.assign(resp.url);
+			 } else {
+				 var tmp = document.createElement("html");
+				 tmp.innerHTML = await resp.text();
+				 const progress = tmp.getElementsByClassName("progress")[0];
+				 document.getElementsByClassName("progress")[0].innerHTML = progress.innerHTML;
+			 }
+		 }
+	 } catch (error) {
+		 console.log(error);
+	 } finally {
+		 setTimeout(refresh, 3000);
+	 }
+ }
+ setTimeout(refresh, 3000);
+</script>
+{{ end }}