Comment 37 for bug 1357321

Here'a yet another one. Hopefully only small bug fixes are needed after this.
https://codereview.qt-project.org/#/c/98547/

This one makes mobile data detection really works and uses property cache instead of making blocking calls for every property call.

The 3 other reviews do not need to be included, two of them only effect mac os x, and the other is for the example app.