Adding the Managing Template window in the templates doc

include/session-templates.html

@@ -20,8 +20,30 @@
   In the <a href="@@newopen-session-dialog">New Session dialog</a>, a panel lists the different
   template (factory and user-created).
 </p>
+
+<h2>Managing Templates</h2>
+
+<figure>
+  <img src="/images/manage_templates.png" alt="The Manage Templates window">
+  <figcaption>
+    The Manage Templates window
+  </figcaption>
+</figure>
+
+<p>
+  Both Session templates and Track Templates can be managed through the Manage Templates
+  window, which can perform the following actions:
+</p>
+<ul>
+  <li>Renaming a template</li>
+  <li>Removing one</li>
+  <li>Adding/modifying its description</li>
+  <li>Exporting the templates (e.g. to be used in another Ardour instance)</li>
+  <li>Importing templates (from e.g. another Ardour instance).</li>
+</ul>
+
+
 <p>
   See also <a href="@@adding-tracks-busses-and-vcas">Adding Tracks and Busses</a>
   for information on templates for individual tracks or busses.
 </p>
-