Copying taxonomy documents should not be allowed

Currently we are able to copy a taxonomy document to the documents (images and assets) folder (see screenshot_1 and screenshot_2). This should not be allowed.

You can reproduce this on the latest taxonomy demo:

1. On the CMS, navigate to Taxonomies/exampletaxonomy
2. On the top menu, select Document and Copy
3. Choose a target folder to copy to
   • The result is that your taxonomy is successfully copied to the chosen destination
   • I wouldn't expect this action to be allowed

EDIT: Move and delete should also be disallowed