New pattern for legacy "inline validation" JS.

I've created a new mockup pattern for the legacy Javascript *inline_validation.js* in *plone_ecmascripts*.

In order for this to work, the widget markup will also have to be changed in plone.app.z3cform and other places for formlib and archetypes.

See also:
* https://github.com/plone/Products.CMFPlone/issues/282
* https://github.com/plone/Products.CMFPlone/issues/299

Ping @thet