Ad banner at top of page on desktop

- [new] ads slots can be out of the context (`#preload-1`)
- [new] if LeadAdTopPageSwitch is on, the lead ad is placed on top of the page on desktop
- [new] Hide all ads if content is ad sensitive

This will not be switched on in production. Design tweaks will be implemented, with CODE as a test environment.

![screen shot 2014-03-11 at 14 53 47](https://f.cloud.github.com/assets/85783/2386532/2c0ca944-a92d-11e3-9019-512f0d6da4d9.PNG)

![ ](http://media2.giphy.com/media/6imitJQNkU78k/giphy.gif)