Create jquery_ujs for plgapp similar to rails one

[mkasztelnik]

Take a look at: https://github.com/rails/jquery-ujs/blob/master/src/rails.js it adds possiblity to define request method type in plain html. E.g. to have working sign out link you can simply create following html:

<a href="/sign_out" data-method="delete">Sign out</a>

This operation also adds CSRF Token to the request.

What is more is can be used to simplify UI creation, e.g. for deleting rimrock jobs:

<a href="/rimrock/jobs/<job_id>" data-method="delete" data-confirm="Are you sure?" data-remote="true">delete</a>

As a conclusion following actions will be performed:

• ajax:beforeSend event is generated (here some spin icon can be presented to the user)
• confirmation alert will be shown to the user. Delete action will be performed only when user clicks "OK"
• ajax query will be triggered with method set to delete
• ajax:success or ajax:error is generated (in this situation user can e.g. remove html element from the page or show error message)

Here you can see simple usage of mentioned mechanism.

/cc @dharezlak, @mpawlik, @bwilk please let me know what do you think about this feature.

[mkasztelnik]

I forgot to mention about CSRF token support - description updated