RSS feed handling

Basic handling of RSS feeds, in KDeclarativeWebView and the QML UI
- KDeclarativeWebView exports a QStringList of RSS feeds
- In the dashboard, there's now an RSS button, which copies the link of
the first feed found to the clipboard

That way, the user can paste it into the RSS reader's add dialog, that
part already works.

Would be nicer to do this through Nepomuk, automatically, but this
already provides a nice base for it