Fix image streaming
Fix image streaming with resize
Fix content size whithout x-send-file

Uses the FilUploader component to manage the file selection and save the file content at same time as the model. Prior to this change, the content was saved as soon as it was selected which is not possible on new records

* Defines extension hooks to use to specify the object type to use as field value and the value to pass when updating the attachment.
* Fixes onchange

Store your image into an external filesystem

This code was initially used to magically know if we need to obfusc or not the filename into the database. Since this option is now explicit, we can safely remove-it. Moreover, without this code it's now possible to migrate old storage_file contents to the new fs_* addons