Update language Portuguese Brazil

[davbrasan]

[hackademix]

Thank you very much for your contribution!

Actually the best way to contribute translations is using this Transifex instance: https://www.transifex.com/otf/noscript/ .

If one prefers to edit the messages.json file manually, the description properties should be kept even if they're empty/redundant, not to cause trouble with the Transifex automated import/export flow.

I'm sorry I forgot to add this information to https://noscript.net/community: I've done it right now :)

I'm gonna merge your changes manually ASAP, thanks again.

[davbrasan]

OK. I used as a base the files messages.json in English to translate.