fix some bugs

CL: fix default value for watermark config in controlpanel
CL: don't do restore thumbnails if title starts with 00-
CL: add watermark as an image file in static :
CL: ++resource++iuem_repository_static/img/filigrane.png
Change watermark managment

CL: since it is possible to view the image without the watermak
CL: when it is done with JQuery, it is necessary to hardcode
CL: the watermark in the image as done previously...
CL: but with a true image