use standard form validation instead of custom json controller's methods, support to apply the commment section component on entity not yet created (will be created with the comment)

[views/json] import dumps from cw.web (which handles the different possible dumps impl. depending on python version or external json packages)

also refactor comment oneline view on the way

refactor: no need for InlineCommentView, nicer id on comment forms. Also properly fix #473629: register/login link should appears on the top of the form when clicking "add comment"

fix #816385 by [re]loading only new/edited comment and properly edit the DOM using js. Also: cleanup javascript, try to put form where the comment will be located (not yet finished)