add 'reset website' form to /user/site-settings.html template.

This is part of the 'danger zone' section in site's settings. The back-end for
this feature is not yet implemented.

templates/user/site-settings.html

@@ -276,6 +276,7 @@
         <p class="be-warning">
             <strong>Be careful here. You can break the website and lose data.</strong>
         </p>
+        
         <form class="be-gui-form"
               action="/danger/repopulate-search-db"
               method="post">
@@ -297,6 +298,28 @@
                 Re-populate Search Database
 	    </button>
         </form>
+
+        <form class="be-gui-form"
+              action="/danger/reset-website"
+              method="post">
+            <input required
+                   type="hidden"
+                   name="AUTHENTICITY-TOKEN"
+                   value="{{token}}">
+            <p class="be-gui-form-hint">
+                This deletes all the User Accounts, Pages, Archive Entries and
+                files you've uploaded to Storage. Use this if you want to wipe
+                the site clean and start again. It, also, clears the 'Search
+                Service' database. 
+            </p>
+            <button class="be-gui-button danger"
+		    title="Repopulate the Meilisearch database."
+		    type="submit">
+	        <img alt="Save nav. menu setting for{{db-data.title}}"
+		     src="/images/icons/reset-website.png">
+                Reset Website
+	    </button>
+        </form>
     </div>
     {% endif %}
 </main>