Allow spaced lines to show in invoice.

When creating an invoice, it shows you can space out lines (or paragraphs) in the item notes when you are editing. However, when you send or preview the invoice, there are no separate paragraphs shown and everything in line after line, making it harder to read and look messy. For example, I have an invoice for the design fees and in the item notes, I have it separated into two sections, one for schematic design details and one for design development, and I would like a single line between the two to separate them and look cleaner.