Spanish translation

Spanish translation from HerculesWS/FluxCP
Translation improvements

Changed some translations to be neutral and friendly between spanish
variations like: es_ar es_cl es_es es_pe es_co etc
User sidebar lang support
Added two missing labels

Re-added two missing labels in es_es.php and en_us.php
Ref. 202b7ea
Minor fix

Fixed a variable name to make the Register link works with lang support.
Fix: News from Facebook page

Fixed an issue getting the RSS xml file from a secure URI under SSL.
Testing environment: OS X with xampp server.
Ref 1. 5ec2229
Ref 2. http://stackoverflow.com/questions/1888268/get-xml-from-https-url
Merge branch 'spanish-translation'
Merge branch 'Facebook-News-Feed'
Translation improvements

Ref.
https://github.com/rathena/FluxCP/commit/c115fea5ef930acf1b434fbebfbe1a2
d4d530760#commitcomment-7470962