Improve sinli import : catalog

For import of books we need to add some changes:

• Modify import process to make it work with to_str method of sinli lib instead of creating a temp file.

• Check product can be buyed.

• The provider of the product will be the contact that sent the sinli email.

• Duplicate barcode to ISBN.

• Author : If we dont find a contact with the name, we create a new one.