Fixes shaarli#1450

THis provides a richer export, incompatible with old browsers, but allowing nicer integration mechanisms into other systems.
I typically gonna use that to generate a lifestream including my Shaarli content.

index.php

@@ -1451,6 +1451,10 @@ function ($item) {
         } else {
             $prependNoteUrl = false;
         }
+        $extendExport = false;
+        if (isset($_GET['extend_export'])) {
+            $extendExport = $_GET['extend_export'];
+        }
 
         try {
             $factory = new FormatterFactory($conf, $loginManager->isLoggedIn());
@@ -1479,6 +1483,7 @@ function ($item) {
         $PAGE->assign('date', $now->format(DateTime::RFC822));
         $PAGE->assign('eol', PHP_EOL);
         $PAGE->assign('selection', $selection);
+        $PAGE->assign('extend_export', $extendExport);
         $PAGE->renderPage('export.bookmarks');
         exit;
     }

tpl/default/export.html

@@ -56,6 +56,22 @@ <h2 class="window-title">{"Export Database"|t}</h2>
         </div>
       </div>
 
+      <div class="pure-g">
+        <div class="pure-u-lg-1-2 pure-u-7-8">
+          <div class="form-label">
+            <label for="extend_export">
+              <span class="label-name">{'Extend import to include thumbnail and permalink|t}</span><br>
+              <span class="label-desc">{'Provide a richer export, unfortunatly incompatible with browsers'|t}</span>
+            </label>
+          </div>
+        </div>
+        <div class="pure-u-lg-1-2 pure-u-1-8">
+          <div class="form-input">
+            <input type="checkbox" name="extend_export" id="extend_export">
+          </div>
+        </div>
+      </div>
+
       <div class="center">
         <input type="submit" value="{'Export'|t}">
       </div>

tpl/vintage/export.html

@@ -17,6 +17,12 @@
           Prepend note permalinks with this Shaarli instance's URL
           <em>(useful to import bookmarks in a web browser)</em>
         </label>
+        <br/>
+        <input type="checkbox" name="extend_export" id="extend_export">
+        <label for="extend_export">
+          Extend export by adding thumbnails/permalinks
+          <em>(Can break import in browser)</em>
+        </label>
         <br><br>
         <input class="bigbutton" type="submit" value="Export">
       </form>