main: Hide DVD menu items when unavailable

https://bugzilla.gnome.org/show_bug.cgi?id=721797
disc-recorder: Hide menu items when unavailable

https://bugzilla.gnome.org/show_bug.cgi?id=721797
screenshot: Hide menu items when unavailable

https://bugzilla.gnome.org/show_bug.cgi?id=721797
grilo: Correct the default model for the icon view
grilo: Don't allow selections to start at the root
grilo: Add code to create a debug tree view
grilo: Empty the playlist when adding new items
main: Add debug code for the playlist widget
libgd: Update from master
grilo: Update for libgd API changes
grilo: Ensure that media is initialised
grilo: Add mtime to the tree store
grilo: Add search button
grilo: Add TotemMainToolbar widget

To be used as the main header bar.
grilo: Use new TotemMainToolbar