Updates portuguese strings.xml as @vreixo requested

on issue #221 - refactoring and reorganising.

- I went back with some decisions (e.g. "personalizada/o" for "custom" instead of "particular")
- I changed the step-by-step verbs to the infinitive
- Also changed some capital letters
- Had careful attention with the hard/slight turn left/right

I hope it's all okay! Let me know if there's any issue with the translations. Keep up the good work!