Improve Spanish locale considerably

Adds some missing spanish translations

Translations up to es.admin_js.admin.flags

Translations up to admin_js.admin.groups

Translations up to admin_js.admin.logs

Translations up to admin_js.admin.users

Translations up to admin_js.admin.user

Finishes admin_js.admin translation to spanish

Adds translation for remaining keys
Merge pull request #1946 from bbonamin/es_locale

Improve Spanish client locale considerably