Scroller: removed 'view port wrapper' since it is no longer necessary
Panel: added optional footer. link to wiki.
docs tweaks
PanelScreen: clipping is turned off by default
Item Renderers: fixed icon and accessory positioning with inifinite gap (closes #460)
Slider, ScrollBar, SimpleScrollBar: sub-component factories invalid after direction change because they will need new skins (closes #393)