Issue #2249723 by andrei.dincu: Create xmlsitemap_engines_test module
Issue #2249723 by andrei.dincu: Created XmlSitemapEnginesFunctionalTest class
Issue #2249723 by andrei.dincu: Put NULL as conditions instead of array() to get all sitemaps
Issue #2249723 by andrei.dincu: Add documentation for XmlSitemapEnginesFunctionalTest methods