prefixes arnold shader search names with 'ai'
Update ShaderMenu.py

bringing the spacing in line with other types (as per john's notes)
Removed MessageWidget.textWidget() method.

The internal text widget should now be considered private. The currently displayed messages may be cleared using the new MessageWidget.clear() method.
Fixed MessageWidget crashes encountered in Maya.

After much stumbling around in the dark, I've thrown in the towel on trying to get block level visibility edits working, and resorted to a simpler approach where messages are stored independently of the text widget.
Removed deprecated MessageWidget.appendException() method.

It has been deprecated for a few versions now and is no longer used within Gaffer. The appendMessage() method is still used by NotificationMessageHandler so remains for now.
Add control over the default button to the OpDialogue.

This controls whether the OK or Cancel button is focussed by default when displaying the Op. The default value is as before, focussing the OK button, but the value can be controlled either by user data in the Op or by passing an alternative argument to the OpDialogue constructor.
Merge pull request #756 from bentoogood/arnoldShaderMenu

Added search prefix to arnold shader names
Merge pull request #767 from johnhaddon/messageWidget

MessageWidget fixes
Merge pull request #768 from johnhaddon/opDialogueFocus

Added control over the default button to the OpDialogue.