Add princeton mouse atlas to last_versions.conf

last_versions.conf

@@ -26,3 +26,4 @@ admba_3d_p4_mouse_16.752um = 1.0
 admba_3d_p14_mouse_16.752um = 1.0
 admba_3d_p28_mouse_16.752um = 1.0
 admba_3d_p56_mouse_25um = 1.0
+princeton_mouse_20um = 1.0