Blender Git Loki

Outliner: walk navigation operator and openclose fixes

Adds a keyboard walk navigation and selection operator to the
outliner. Up and down arrow keys walk up and down the list of
elements, and left and right will open and close elements if
the elements are closed or opened respectively. Holding shift
while walking up and down the tree expands the selection.

Holding shift while clicking or pressing left and right arrows
will expand or collapse all children elements recursively.
Pressing enter to openclose the hovered element is removed.

Also allows click+drag for openclose of element subtrees.

This moves openclose toggling to the openclose operator to
remove duplicate code. The outliner tree building is tweaked
slightly to set the proper parents in scene display mode for walk
select to walk to parents without errors.