Update portuguese.json

Blockchain.info/pt is set by clicking Portugal's flag on the Language menu, but rather than getting the correct Portuguese(PT) from Portugal, we get Portuguese(BR) from Brazil.

So just trying to help, i've done a full review, some typo fixing and translation BR/PT of the file "portuguese.json". You should definitely save your current one, but please display it under the right brazilian flag.

If you find this more appropriate or any useful at all, feel free to use it.
Thanks

Just in case this worths something...
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