Ability to change modal form backdrop element behavior

[OpenStack Infra]

https://review.openstack.org/113206
commit a6c364448a4bbbe4372769de3edb9c8f384ce00f
Author: Timur Sufiev <email address hidden>
Date: Mon Aug 11 13:54:20 2014 +0400

    Ability to change modal form backdrop element behavior

    By default modal form is closed after clicking outside of it on a dark
    backdrop (data-backdrop="true"). For the forms with a lot of fields
    this could lead to a loss of data the user had entered before he has
    unintentionally clicked outside of the form. So more preferable option
    for such forms (and workflows/client-side modals) would be
    data-backdrop="static".

    DocImpact
    Change-Id: I56fca9131a4e4d3991d53184ee1332e84138cdc2
    Partially-Implements: blueprint form-template-to-view
    Related-Bug: #1062065

[Tom Fifield (fifieldt)]

Basically, this is documented in the horizon devref, where basically all the docs for customising live