Issues with material renaming

Few issues related to renaming .materialdef via inspector's name field:

• The object name of all materials in the scene graph that refer to the renamed material is updated to match the new name. This happens even if you have manually changed the object name of some of those material objects. It should probably be forbidden to change the name of the material object of referenced materials and instead always show the referenced material name.
• The name field on the inspector immediately reverts back to the previous value on rename. The file name and names of the referring material objects are changed correctly.
• White "in use" highlight is lost when the .materialdef is renamed. It'll reappear once you save the presentation or doubleclick on the .materialdef again.