Without this, each call to getContentType modifies and reindex the object

 With this change, by using "None" instead username at any SecurityTestCase
 assertion, it test security as Anonymous. ie.:
   self.failIfUserCanViewDocument(None, document)

Else it is not possible to use newContent with temporary portal types.

If it is not imported, then it won't appear

- getting document original content if format is empty
- conversion raster image -> svg

Make user current user is allowed to copy or move object by checking this security permission explicitly.

Previously, portal_type parameter was passed in REQUEST and stored in the selection for the next listbox, which can be listing objects of another portal_type