MDL-46817 behat: Table selector support css

Previously table selector supported id and caption only.
But in few cases we don't have proper id, so added support
for css

lib/behat/classes/behat_selectors.php

@@ -110,6 +110,9 @@ XPATH
         , 'filemanager' => <<<XPATH
 //div[contains(concat(' ', normalize-space(@class), ' '), ' ffilemanager ')]
     /descendant::input[@id = //label[contains(normalize-space(string(.)), %locator%)]/@for]
+XPATH
+        , 'table' => <<<XPATH
+.//table[(./@id = %locator% or contains(.//caption, %locator%) or contains(concat(' ', normalize-space(@class), ' '), %locator% ))]
 XPATH
     );