Added checks to the following areas
* half the material buttons
* multires, shapekeys, vert groups
* renaming a linked Object in the links could loose the object on next reload.
Made center functions check for library data as well as changing
the way it works.
Rather then centering all objects in the selection and stopping if it finds libdata, or a multiuser mesh.
It centers all that it can, and reports any objects that didnt center and why.
54efb4c916