Fixes 6546 - Swap the contents of default.tmpl and empty.tmpl in the test suite

tests/expected_output/en/sitemap

Index: tests/expected_output/en/sitemap
===================================================================
--- a/tests/expected_output/en/sitemap
+++ b/tests/expected_output/en/sitemap
@@ -1,25 +1,16 @@
 
 
 
 
 <h1> Unfiltered </h1>
 <ul>
-  <li>title : filter </li>
-  <li>title : get_page_url </li>
-  <li>title : global </li>
   <li>title : includer </li>
-  <li>title : translate </li>
-  <li>title : translate-html </li>
-  <li>title : translate-include </li>
-  <li>title : translate-not-enough </li>
-  <li>title : translate-partial </li>
   <li>title : translate-template </li>
-  <li>title : translate-tmpl </li>

[Sebastian Noack, 2018/04/03 22:32:51]

So these pages showed up here before because they defined any metadata (i.e. the
template), but since they didn't define any other metadata they are no longer
considered by get_pages_metadata(). I still fail to see why these semantics make
any sense. But not my business, and somewhat unrelated of this change anyway.

[Vasily Kuznetsov, 2018/04/03 22:47:04]

I pretty much see it the same way as you do, but there's another possible point
of view: `get_pages_metadata` returns user-defined metadata dicts from the pages
that have user-defined metadata. Arguably it's less consistent, but in practice
(and for real use cases of this function) it makes no difference because all the
pages that people would ever want to get out if it would have user-defined
metadata. Julian (who actually uses CMS and this function) prefers second
interpretation and I think this is not important enough to have debates about,
so I'll just let it be.

[rosie, 2018/04/04 16:22:17]

Should there be a comment somewhere in this file that makes the expected
behavior clearer?

[Sebastian Noack, 2018/04/04 17:42:57]

As I pointed out in the other review, there is a comment in the source code:
https://hg.adblockplus.org/cms/file/b683e321a9d0/cms/converters.py#l477
But its merely indicating that pages without custom metadata are skipped, but
fails to explain why.

Furthermore, it seems there is out-of-source documentation for provided template
functions in docs/api/functions.md, which however is missing any mention of
get_pages_metadata() at all.

   <li>title : sitemap </li>
 </ul>
 
 <h1> Filtered </h1>
 <ul><li>title : sitemap </li>
 </ul>
 
 <h1> String Filter For Listy Option </h1>