[+] MO : Watermark : Show nonwatermarked image for logged in customers

Part 1
This allows customer that are logged to see the images without watermark.
To prevent users to just add something like -nonwatermark to the path. I added a hash at install and at hook execution if no hash exist.
The hash is permenent and not deleted at uninstall, allowing owners to re-install the module, and don't need to generate images again.

Part 2 - https://github.com/PrestaShop/PrestaShop/pull/2063
Hi.

It's done.