feature for iframe propogate events out

[lintaba]

this adds support for iframes to send their data to the parent frame.

also, same-origin should keep the payload safe

[barryvdh]

What would this do?

[lintaba]

A few projects ago we used a lot of business logic inside iframes. We needed a way to add them to the debugbar. (a bit like it happens with ajax+headers).
The debugbar is opened in the top frame, and when something happens inside the iframes, the changes are being added to the top-level debugbar.

For me it was useful, and used a lot. Just wanted to contribute it back to the community :)

[parallels999]

Fixed on #615