gnome-keyring Review: GcrComboSelector and GcrTreeSelector

[Stef Walter <stefw collabora co uk>]

I've done some work on implementing a combo and tree based selectors in
libgcr:

https://bugzilla.gnome.org/show_bug.cgi?id=649989

 * GcrComboSelector allows selecting one object at a time
   and uses 'markup' property to display the object.
 * GcrTreeSelector uses various columns, and a checkbox so that multiple
   objects can be selected at once.
 * Add images for both of the above.
 * Derive directly from GtkComboBox and GtkTreeView respectively.

This is progress towards implementing the gnupg chooser in libgcr.
Anyone interested in reviewing this code?

Cheers,

Stef