DB: Add Hardware.get_rating API
Frontend API: Introduce /api/device.html endpoint

(Yep, that's an API returning HTML)
Frontend API: Document rate()
Frontend: device.html markup for visual feedback of rating
Frontend: Update device DOM node on successful rating
Frontend: don't autofocus search field if on results page
DB: get_timestamp: throw microseconds away. We're not the Stasi.
Frontend: Introduce generic way to render contributions