Fixed SceneView expansion bug.

The correct Context wasn't being used to evaluate the children of the selection, meaning that if the viewed Nodes used any context variables or where time dependent, errors would occur.

Fixes #438.
Fixed RenderManShader to accept inputs from coshaders in Boxes.

Fixes #440.
Fixed Menu search compatibility with Qt 4.6.

We were using the QLineEdit.setPlaceHolderText() method which didn't exist until Qt 4.7.
Merge pull request #441 from johnhaddon/sceneViewExpandContext

Fixed SceneView expansion bug.
Merge pull request #442 from johnhaddon/rendermanShadersInBoxes

Fixed RenderManShader to accept inputs from coshaders in Boxes.