Edit purchase order number and expiration date #56887

http://pm.tablexi.com/issues/56887

I refactored the way the new/edit form for accounts is handled. Basically, each account type has two views for what fields to display: one for new accounts only, and one for new and edit. 

It's going to make it much easier to add payment types if we need to and move fields between create-only and always editable.