Double click shield breaks jsf pages which are outside the theme

JSF pages having h:form but not using the theme (typically some error pages) causes javascript error in browser.

This is because the jquery.nuxeo.doubleclickshield.js is not provided while the h:form renderer (NxFormRenderer) appends the doubleClickShield activation at the beginning of the rendered form:

<form id="xxx" ...>
  jQuery("#xxxxx").preventDoubleSubmission();
  
  ...
  
</form>

and of course preventDoubleSubmission will be unknown.

A solution would be:

1. instead of appending the activation at the beginning of each form, the NxFormRenderer should just mark the form as requiring the shield. This could be done with a css class "doubleClickShielded". In case, jquery.nuxeo.doubleclickshield.js is not provided, this won't cause any errors.
2. do a global activation in the jquery.nuxeo.doubleclickshield.js file adding

   jQuery(document).ready(function() {
     jQuery('form.doubleClickShielded').each(function() {
       jQuery(this).preventDoubleSubmission();
     });
   });
   

   This is much nicer and efficient because, instead of calling many times the activation (once per form), we will do it globally on document ready.