Proper URI-encoding in InternalServer::build_redirect()

- Before this change `InternalServer::build_redirect()` only URI-encoded the
  article path, ignoring the book name and/or the root location components of
  the URL.

- In order to be able to test this fix, corner_cases.zim was renamed to
  contain a couple of special URL symbols in its filename. The
  `create_corner_cases_zim_file` script was updated accordingly.

test/meson.build

@@ -34,7 +34,7 @@ if gtest_dep.found() and not meson.is_cross_build()
       'example.zim',
       'zimfile.zim',
       'zimfile&other.zim',
-      'corner_cases.zim',
+      'corner_cases#&.zim',
       'poor.zim',
       'library.xml',
       'lib_for_server_search_test.xml',