Spanish update and technical corrections...

* Follow Spanish grammar rules:
 - Only uppercase at the beginning of the phrase and names.
 - Less is more
 - `Settings == Settings` and not `Settings == Configuration`;  
  a bunch of better contextualized words are there for using them.
 - Don't _ever_ say please, golden rule.
* Add arrows to clarify page navigation with minimum space.
* Use correct nomenclature for technical terms;  
 leaving them understandable for the power user.
 - Never, ever translate for the sake of translating, menus have to be usable.