Make API apps search follow docs for dev/device parameters (bug 1060062)

This fixes incoherencies between the API and the docs regarding `dev` and `device` parameters. They are super confusing, but I need them to be coherent for https://bugzilla.mozilla.org/show_bug.cgi?id=1060062

This patch make the API match what fireplace is sending and what the docs are specifying. The rocketfuel and feed API were already doing the right thing.
Invalid what?