Create language folder and ask the user for the language variable

Asks the user for the wp_language variable and creates the language folder inside the wp-content. This not download the language files from http://translate.wordpress.org. 

A future feature it could be to obtain the files via curl from the following urls :

http://translate.wordpress.org/projects/wp/dev/admin/network/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/admin/network/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/admin/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/admin/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/twentytwelve/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/twentytwelve/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/twentythirteen/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/twentythirteen/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/twentyfourteen/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/twentyfourteen/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/twentyten/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/twentyten/es/default/export-translations?format=po

http://translate.wordpress.org/projects/wp/dev/twentyeleven/es/default/export-translations?format=mo
http://translate.wordpress.org/projects/wp/dev/twentyeleven/es/default/export-translations?format=po

where 'es' is part of the language variable... the problem is the urls changes from one language to another... for example, portuguese it´s not 'pt-pt/', it´s only 'pt/'. 

Languages can be checked from here http://translate.wordpress.org/projects/wp/dev