Groups can now be collapsed and re-expanded.

(cherry picked from commit 9e8d5600557e2d115338a9b173f940065248ed27)

src/widgets/group_widget.h

@@ -31,6 +31,7 @@ enum GroupListWidgets {
 	WID_GL_CREATE_GROUP,             ///< Create group button.
 	WID_GL_DELETE_GROUP,             ///< Delete group button.
 	WID_GL_RENAME_GROUP,             ///< Rename group button.
+	WID_GL_COLLAPSE_EXPAND_GROUP,    ///< Collapse/expand group button.
 	WID_GL_REPLACE_PROTECTION,       ///< Replace protection button.
 };