clean blend file to improve linked and append from old blend files

As in the case of the reused source code, I re-use the blender files and modify them, improve them, and then save them to have more work possibilities. As far as I know, it's an older bug and it can be seen if you open a new file and then link or append to another blender file that has been processed several times. In this case, it is observed that materials and actions that were used in the past in the old file appear. My opinion is that these leftovers should be able to be processed and removed in order not to find a huge pile of materials and actions ... in case we do a link sau append. This improvement will allow the files saved from other blend files to be cleaner, and easier to use when append au linked to a blend file.

As a conclusion, a tool or a possibility to display the content as we see when we link or append and the possibility of removing what we don't want to save would be necessary.