Dialog: modified the dialog close button icon and icon position.

[thorikiri]

enabled to change dialogs close button icon and icons position.

[gabrielschulhof]

Thanks a lot for the pull request. We have, in the meantime, by fixing #3886 made it possible to prevent the dialog from creating a close button at all. This, in turn allows you to add a close button to a dialog by hand, meaning that all the flexibility provided by the button creation HTML is now at your disposal. Starting with at least 1.3.0 you will be able to simply

<div data-role="dialog" data-close-btn="none">
  <div data-role="header">
    <a href="go/to/some/page.html" data-role="button" data-icon="plus" data-iconpos="left">Custom button</a>
  </div>
</div>

and the dialog widget will not add a close button to the dialog, so the button you create yourself can play the role of the close button.

This pull request, as well as #5117 are evidence that there is a significant need to customize the button(s) in a dialog's header. We believe the best way to do that is to provide an option that prevents the dialog from adding its own button, because that enables solutions such as the one above and makes it unnecessary to pass information about the buttons in the dialog's header into the dialog via its options.

[thorikiri]

Thank you. I'm looking forward to 1.3.0.