MDL-39348 behat: Removing redundant step

This is causing some browsers to fail tests
as they uses the DOM of the current page to
search "You are logged in as".
MDL-39348 behat: Changing to correct activity names
MDL-39348 behat: Chaining strings instead of splitting strings in lines
MDL-39348 behat: Switching to wait which does not conflict with IE

Also solving bug with DOM ready, timeout
was set to self::TIMEOUT miliseconds not
seconds.
MDL-39348 behat: Compatibility with Safari and IE

Also changing from SeleniumDriver checking
to GoutteDriver as is less probably to change
goutte than to change selenium.