Various tweaks and fixes

Xero Integration
- adjusted integration to allow invoices in an 'Awaiting Payment' status to still be edited and resubmitted within Factory.
Xero Integration
- added an alert when attempting to edit an invoice in Factory that has partial or full payments applied to it in Xero.
Other
- added an option under
Settings > Integrations
to show/hide accounting codes on orders and PDFs.
Other
- line breaks in the descriptions of once-off products and notes will now be reflected correctly on all PDFs.
Other
- you can now add line breaks to pricing table values.
Fix
- fixed an issue causing inventory levels to incorrectly adjust when Orders are converted back to a Quote.