[imp] Implementing the choice to not use a language cookie in multilanguage

This replaces 
https://github.com/joomla/joomla-cms/pull/4911
To test all conditions, create a default multilanguage site with 3 languages. 
Set the default site language to en-GB.
Makes sure the default Browser language is not en-GB.
Set the language filter "Cookie Lifetime" to None
Set for each test the "Language Selection for new Visitors." to Site language or to Browser Settings.

Load the home page of the third language.
DO NOT CLOSE IT.
Create a new tab or a new window <b>in the same browser</b>
In that page, load the pure url of the site http://mysite.com

This should display the language defined by the "Language Selection for new Visitor".

Please also test on a site where you first have displayed the third language without the patch and cookie was set to Year or Session.