Support transparent dialog backgrounds

[tqc]

This change allows the dialog to work more like a standard dialog when the device screen is significantly larger than the dialog content.

When transitioning to a dialog, the class ui-dialog-background is added to the previous page so that it will remain visible if the background of ui-dialog is set to transparent rather than black.

The background page may also need data-dom-cache set to prevent it from being removed - there doesn't seem to be an easy way around that without significantly complicating the timer call that removes hidden pages.

[tqc]

Additional change unrelated to the original pull request - add swipeup/swipedown events and add a data parameter to the swipe event trigger so that multitouch gestures can be detected and handled differently if necessary.

[scottjehl]

Great idea. Added to the feature requests page https://github.com/jquery/jquery-mobile/wiki/Feature-Requests

[skang]

Absolutely agree!!! Some users find it quite annoying (even angering) to be deprived of the context page view when a dialog shows up with empty background.

[xmkevin]

Yes, this is what we want. but he latest release is not support it.

[tqc]

I'm now using a modified version of this which doesn't require modifying jquery mobile itself:

http://tqcblog.com/2012/04/19/transparent-jquery-mobile-dialogs/

[serbanghita]

Hello,

Why is this closed, is is available in a dev release?

[marceloverdijk]

Also wonder if this is implemented or not. I'm using 1.1.1 but can't find anything in the docs related to transparent dialogs...