* change the label field to not display the error text by default
* change all html5 fields (input, select, textarea) to add a custom *invalid* class when the field is invalid
* change all html5 fields to listen to the `focus` and `blur` event (with the renderjs onEvent method)
  Then, acquire (with `declareAcquiredMethod`) and call `notifyFocus` / `notifyBlur` methods respectively.
* change the label field to handle `notifyFocus` / `notifyBlur` (with `allowPublicAcquisition`).
  Change the validation error text display state depending on the field status
* Trigger onStateChange to set invalid class. If error comes from input field, we need to change state locally to set invalid class
* Regenerate gadget_erp5_nojqm.css from  erp5less.css using http://lesscss.org/less-preview/
* Textarea gadget should not prevent default when invalid event is triggered
* Support notifyFocus and notifyBlur in panel