Improve ajax call to build page url slug

* Disable form submission until ajax request has finished
* Don't do ajax request if page name is the same as the previous ajax
  request
* Take in account the ajax response (success of fail) only if it's for the
  last ajax request.
add jHandle support
Merge pull request #1388 from Remo/job-handle

add jHandle support
Merge pull request #1340 from mlocati/fix-slug-ajax-build

Improve ajax call to build page url slug