Improve resizable node rendering

* Only place them in a high z-index while resizing so they don't render
  above dialogs and menus
* Add resize transition

ve.ce.ImageNode.js
* Switch from element attributes to CSS for setting dimensions

ve.ce.Node.css
* Add resizing class for resizable nodes for z-index
* Add transitioning class for resizable nodes for transitions
* Switch from border to inset box-shadow to not affect handle position
  calculation

ve.ce.ResizableNode.js
* Add/remove resizing class while resizing
* Switch from using $image to $resiable to make the class useful for
  non-image node
* Enable transition and set new dimensions before transaction processing
  which will cause re-rendering)
* Delay transaction processing for resize until after transition is
  complete
* Add hiding of context menu on resize start

ve.ce.Surface.js
* Add getSurface method so we can get to the context menu

Change-Id: I4667e394d0af4a80b651c2a0f6d11d30e196bf60
Merge "Improve resizable node rendering"