[Plugin: Web Invoice – Invoicing and billing for WordPress] Separate language from code

Hi.
I’m translating some parts of the plugin to spanish and italian.
I think that, when you’ll publish an update, I’ll loose all my modifications, because language is one with the code of your plugin!

It would be great to separate text strings from code, so when you update the plugin, translated text could remain.
Could you give de ability to edit string text from the control panel, with a form?

http://wordpress.org/extend/plugins/web-invoice/