Translation to Portuguese (Portugal)

Finally! Here's the translation to Portuguese! It was a little more
difficult than I expected but what's done is done, thanks to the help of
a great friend Rosa!

I hope there is no problem with the translation. I did my best, but I'm
not a professional! :)
I think it's translation can be used in several Portuguese language
speaking countries (example: Brazil, Angola, etc.), but, as we all have
different sentence structures (Brazilians, Angolans, etc), there may be
some problems of understanding.

Pedro Costa
Update pref_strings.xml
Update strings.xml
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Merge pull request #11 from P-Costa/master

Translation to Portuguese (Portugal)