Add function to export script and current state ready for conversion to screen grab

[bentoogood]

To simplify the process of generating screen grabs it would be handy to be able to reproduce a UI state including the panel layout, viewer zoom and pan, node selection, scene item selection.
Documentation authors should be able to setup a session showing exactly the contents desired and then export that to some file for later loading by the screen grab image generator function.

[andrewkaufman]

Not sure if it's possible, but It would be nice is such a feature could also keep popup menus open (which typically disappear when you click on anything else.

[bentoogood]

Reference - snippet to get the current layout and stash it as a string. Then eval that string to restore the layout.

scriptWindow = GafferUI.ScriptWindow.acquire( script )
layoutStr = repr( scriptWindow.getLayout() )

#script is called scriptNode in layout string
scriptNode = script
layout = eval( layoutStr  )

scriptWindow.setLayout( layout )

[bentoogood]

Addressed as a user script to export all relevant data.