[PengeAppsPane] Switch to using "bookmarks-changed" signal
[PengeAppsPane] Switch to using "bookmarks-changed" signal

Rather than using the bookmark-added/bookmark-removed signals and refreshing
the whole set anyway use the better "bookmarks-changed" signal.

meego-netbook-ux/meego-panel-myzone,kkszysiu/gnomesocial,meego-netbook-ux/meego-panel-myzone,kkszysiu/gnomesocial