Adds help menu entry for launching documentation resources.
Adds help menu entry for launching documentation resources.

* Body of new menu is defined in startup/gui as this content appears specific to main app
* Declares a placeholder for example-script launching, ready for future implementation.
* uses webbrowser module to perform launching as my research suggests that is the most platform independent approach.
** for best results users would need to set $BROWSER env var, otherwise it's a bit of a gamble what app launches the files

goddardl/gaffer,boberfly/gaffer,cedriclaunay/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,ivanimanishi/gaffer,ivanimanishi/gaffer,hradec/gaffer,ImageEngine/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,chippey/gaffer,paulondc/gaffer,boberfly/gaffer,lucienfostier/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,chippey/gaffer,chippey/gaffer,davidsminor/gaffer,ivanimanishi/gaffer,hradec/gaffer,chippey/gaffer,paulondc/gaffer,lucienfostier/gaffer,boberfly/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,paulondc/gaffer,johnhaddon/gaffer,boberfly/gaffer,GafferHQ/gaffer,hradec/gaffer,goddardl/gaffer,hradec/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,andrewkaufman/gaffer,appleseedhq/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,hradec/gaffer,davidsminor/gaffer,davidsminor/gaffer,paulondc/gaffer,johnhaddon/gaffer,cedriclaunay/gaffer,andrewkaufman/gaffer,davidsminor/gaffer,goddardl/gaffer,cedriclaunay/gaffer,cedriclaunay/gaffer,goddardl/gaffer,johnhaddon/gaffer