images: successor of task-xserver is packagegroup-core-x11-xserver

error message is something like:

ERROR: Required build target 'xfce-nm-image' has no buildable providers.
Missing or unbuildable dependency chain was: ['xfce-nm-image', 'packagegroup-xserver']

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>

recipes-angstrom/packagegroups/angstrom-packagegroup-gnome.bb

@@ -16,6 +16,6 @@ RDEPENDS_${PN} = " \
 "
 
 RRECOMMENDS_${PN} = " \
-   packagegroup-xserver \
+   packagegroup-core-x11-xserver \
 "
 

recipes-angstrom/packagegroups/angstrom-packagegroup-gnome3.bb

@@ -16,6 +16,6 @@ RDEPENDS_${PN} = " \
 "
 
 RRECOMMENDS_${PN} = " \
-   packagegroup-xserver \
+   packagegroup-core-x11-xserver \
 "
 

recipes-images/angstrom/systemd-gnome-image.bb

@@ -5,7 +5,7 @@ IMAGE_INSTALL += " \
 	packagegroup-gnome-apps \
 	packagegroup-gnome-themes \
 	packagegroup-gnome-xserver-base \
-	packagegroup-xserver \
+	packagegroup-core-x11-xserver \
 	packagegroup-gnome-fonts \
 "
 

recipes-images/angstrom/xfce-nm-image.bb

@@ -5,7 +5,7 @@ CONMANPKGS = "networkmanager network-manager-applet"
 IMAGE_INSTALL += " \
 	packagegroup-xfce-base \
 	packagegroup-gnome-xserver-base \
-	packagegroup-xserver \
+	packagegroup-core-x11-xserver \
 	packagegroup-gnome-fonts \
 	angstrom-gdm-autologin-hack angstrom-gdm-xfce-hack gdm gdm-systemd \
 	angstrom-gnome-icon-theme-enable gtk-engine-clearlooks gtk-theme-clearlooks angstrom-clearlooks-theme-enable \