Add ability to create ad hoc invoices (not attached to product)

As with most hosting/IT companies, we constantly generate one off invoices for services like Web Development, I.T. work, etc…

Having to attach it to a product does no good, as there is no way to include a description of services provided on the invoice, and also inundates the users account with tens’s or even hundred’s of products. This is just not feasible.

Please add the ability to simply add a invoice or billable item to the users account.