Improved margins es_ES translation
Fixed bug #807: Margins modules with orders2invoice does not respect cost price
Also, removed duplicated requires in orderstoinvoice.php
Converted indentation to tabs
Updated changelog
Merge pull request #831 from marcosgdf/translations

Improved margins module es_ES translation
Merge pull request #830 from marcosgdf/bug-807

Fixed bug #807: Margins modules with orders2invoice does not respect cost price
Improved margins ca_ES translation