Export: allow prepending notes with the Shaarli instance's URL

Relates to #102

Additions:
- application:
  - export: allow prepending note permalinks with the instance's URL
  - test coverage

Modifications:
- export template: switch to an HTML form
  - link selection (all/private/public)
  - prepend note permalinks with the instance's URL

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

tpl/export.html

@@ -5,15 +5,21 @@
   <div id="pageheader">
     {include="page.header"}
     <div id="toolsdiv">
-      <a href="?do=export&amp;selection=all">
-        <b>Export all</b><span>: Export all links</span>
-      </a><br>
-      <a href="?do=export&amp;selection=public">
-        <b>Export public</b><span>: Only export public links</span>
-      </a><br>
-      <a href="?do=export&amp;selection=private">
-        <b>Export private</b><span>: Only export private links</span>
-      </a>
+      <form method="GET">
+        <input type="hidden" name="do" value="export">
+        Selection:<br>
+        <input type="radio" name="selection" value="all" checked="true"> All<br>
+        <input type="radio" name="selection" value="private"> Private<br>
+        <input type="radio" name="selection" value="public"> Public<br>
+        <br>
+        <input type="checkbox" name="prepend_note_url" id="prepend_note_url">
+        <label for="prepend_note_url">
+          Prepend note permalinks with this Shaarli instance's URL
+          <em>(useful to import bookmarks in a web browser)</em>
+        </label>
+        <br><br>
+        <input class="bigbutton" type="submit" value="Export">
+      </form>
       <div class="clear"></div>
     </div>
   </div>