Freeze break request to improve context menu

[Peter Harvey <peter a harvey gmail com>]

Hello,

The attached patch for Epiphany improves the context menu for bookmarks
and other widgets on the toolbar. It also corrects some related bugs
with the appearance and sensitivity of items on the context menu.

It has maintainer approval. Screenshots available at:
  http://home.exetel.com.au/harvey/epiphany/060215/

Thanks,
Peter Harvey.