FLUID-5276: Show and hide using "fl-demoMenu-hidden"
FLUID-5276: Remove the code to hide on lose focus

The experience is not great as the menu is closed whenever focus leaves
independent of where it goes. Including to the browser chrome or to
another window.
FLUILD-5276: Fixed a bug where a vertical scrollbar would remain after the menu has been put off screen. Fixed the transition so that the background of the menu would slide in instead of popping in. Changed the way the star button was positioned and styled.