Spanish Translation

Hello,

I've done a first version of the Spanish translations.

While doing it I've noticed some issues you might consider: 

* Sometimes sub-articles are called as such, others child articles. In the spanish translation I've used sub-articles primarily.

* Internal details are informed which can confuse some users:
 - "The owner, usually the creator ..." Is it totally necessary to inform that ?
 - " The permission system functions like UNIX permissions" Do all users know about UNIX at all ?

* I preferred writing public access instead of 'others' 


best,