Rename direction components for tip plugin...

Instead of geographic directions, use the basic,
'planar' ones: top, right, bottom, left. The
original convention was picked up from plugins
like Prototip and qTip. We are working in a 2D
space and the UI isn't a map.
Add _wrapStealthRender for tip plugin and refactor.
Clean up tip plugin's cursorHeight aspect...

It needs to be split into another aspect stemSize,
which uses a new detection method by checking the
tip content container's offset.