Added support for different button layouts.
Merge remote-tracking branch 'Harrigan/master'
Added extendablepanel.

Removed panellist.
Reverted accordion.
Vertical layout ignores invisible.
Layouts children visibility support.
Accordion uses visibility instead of add/remove child.
Checkbox Event.CHANGE fixed.
Added child percentWidth to horizontalContinuousLayout.
Merge remote-tracking branch 'Harrigan/master'

Conflicts:
	samples/expandable_panel/application.xml
	src/haxe/ui/toolkit/containers/Accordion.hx
	src/haxe/ui/toolkit/containers/PanelList.hx
	src/haxe/ui/toolkit/controls/Image.hx
Merge pull request #58 from ProG4mr/master

ExtendablePanel, layout child visibility and others.