add CWProperty for_user CWUser when on the user primary view

move CWProperty rtags from autoform to cwproperties module.

fix Bytes submission pb on POST, due to multiple call to field.process_form_value for a same field. In the case of file, stream.read() doesn't return file's data the second time (since the cursor is at the end of the file). Fix this by having a generic process_form_value method that cache field's value in form.formvalues[field] and so _process_form_value is only called once. You should then override that later method on custom fields.

must skip internal field value from the generic relations combobox