Update row and column widgets to set data attr on modal div

https://www.pivotaltracker.com/story/show/79230578

These changes are required to pass the widget's name into the CMS in such a way that Ember can know about it and adjust the heading of the relevant modal dialogue accordingly. With a big assist from @dpetersen we cooked up a way to use a data attribute on the modal's div to store an Ember object, which can then be observed from within the CMS when it gets modified here. Relevant PR in CMS is 

https://github.com/G5/g5-content-management-system/pull/463