[REF] Add a dedicated Adapter for Image and remove the update_image from the ProductCategoryAdapter
[REF] refactor category image export. Use a dedicated connector unit, simplify the image management on OpenERP (we will use only one image per category, it's fit with 90% case and the UI is simplier), custom module can add support of thundmail easily. Add unit test for the category export
Merge branch '7.0_base_catalog_export' into 7.0_catalog_export