Allows multiple inclusion of Card.js

1.  Description of change
    Check that if Card.js Iframe is already created then use the existing one, otherwise create new.
    Add ‘active’ attribute to form object to check that which form the opened popup belongs to. This is for the case that multiple Card.js scripts are included in the same page.
2.  Objective reason
    To allows multiple inclusion of Card.js in one page
    Related PT Ticket : https://www.pivotaltracker.com/story/show/83640854
3.  Developers affected by the change
    All
4.  Impact of the change
    User can include many Card.js scripts
5.  Priority of change
    Normal
6.  Alternate solution (if any)
    None