update gWidgets vignettes to gWidgets2

[landroni]

Related to some minor confusion in http://stackoverflow.com/questions/25513254/how-to-add-a-context-menu-to-a-gframe .

It would be nice if you could "port" the gWidgets vignettes:
http://cran.at.r-project.org/web/packages/gWidgets/vignettes/addingToolkit.pdf
http://cran.at.r-project.org/web/packages/gWidgets/vignettes/gWidgets.pdf

to gWidgets2, outlining in the process the major differences between the two versions. This would be handy, for instance, if one wanted to port a gWidgets package (e.g. latticist) to gWidgets2.

[jverzani]

Can't disagree. I'm leaving this open, but it might be some time before I get around to it. Pull requests are very welcome :)