Changed the data model/ UI form for Invoices and CourseRegistrationCodes
fix up some wording and unicode issues

fix tests given change in the CSV download
Merge pull request #4807 from edx/cdodge/touch-ups

fix up some wording and unicode issues
Merge pull request #4804 from edx/muhhshoaib/Ex-66-change-data-model-UI-form-for-invoices-and-CourseRegistrationCodes

Changed the data model/ UI form for Invoices and CourseRegistrationCodes