FR: Power search text box background string

The name and content search have a little grayed out text in them which sayas what searhc is currently active. The power search does not. Although this is not totally necessary, as you can only be in power search when you enabled it, I still think it would be a good reminder what search you actually have.

Particular useful if you combine it with the feature request to cycle through all three searches on the main search page.