Add dialog motion effects for iOS 7

[dingosky]

As previous, adding motion effects for iOS 7. But no longer assume iOS 7.

Fixes:

• Use motion effect only if iOS 7.
• Apply motion effects to the dialog view, not the full screen view being used for "modal" purposes.

Note this is a fresh, new branch directly off your master. Same name as previous, but it is a new branch. I chose not to apply the "fix" to the two issues you raised on that previous branch since I had made refactoring changes on my other branch and rebasing would have been more difficult that this route (a new branch with the same name). I can, of course, only get away with this slight of hand since no one but me had pulled either of my two branches.

[wimagguc]

Thanks @dignosky, this is awesome :)