Enhancement/image support

Here is a PR to : 
Add image support : now you can import image directly via Soap.

Enhance benchmark : 
- Add a method to benchmark image import.
- Add a method to benchmark localizable products.
- Add possibility to send bulk of entities to Magento. That's how I benchmarked that is better to send calls of 2500 rows to be sure to keep a rate of transfer above 70rows/second.