Ability to hide caret on screenshots (aka fix Bug213 again)

In issue #4 all `assertj-swing` tests failing were fixed. But this one still needs to be fixed.

It was originally issued [here](http://code.google.com/p/fest/issues/detail?id=213)

And as I analysed this issue isn't working well, yet. IMO calling `caret.setBlinkRate(0);` when hiding the caret before taking the screenshot is necessary.

I would like the possibility to change in a test if the caret should or shouldn't be visible on a screenshot.

Inizia tracciando la cattura degli screenshot e la gestione della visibilità del caret trattate nell’issue #4, quindi esamina i test assertj-swing che espongono ancora Bug213. Verifica in che modo caret.setBlinkRate(0) influisce sullo stato nascosto e definisci l’impostazione a livello di test in modo che gli screenshot possano includere o omettere il caret in modo coerente.

Scritto dal modello di indicizzazione a partire dal testo della issue.