Make sample config just have the HS config

The other options are things people usually won't need or want to
set, so just keep it to the basics.

 * Rename config sample to match element-web
 * Update / simplify build instructions
 * Rename nginx config file to differentiate it from EC config

config/nginx.conf

@@ -0,0 +1,10 @@
+server {
+    listen       8080;
+    server_name  localhost;
+
+    location / {
+        root   /app;
+        try_files $uri /$uri /index.html;
+    }
+}
+