Simplifying hideButton('x', false) as showButton('x')

Conflicts:
	src/flash/com/longtailvideo/jwplayer/view/components/ControlbarComponent.as
Html5 casting icon to use same logic as mute button
- utils.addClass and utils.removeClass now accept arrays
- map added to jwplayer._
Improving utils.removeClass and adding two underscore.js
specifically _.filter and _.difference
Further update to utils.addClass
It will no longer add a class which is already present on the element.
Merge pull request #153 from jwplayer/bugfix/flash-cast

Html5 casting icon to use same logic as mute button