Dropship checkbox is added to the SO edit form
- unchecked by default
- if checked then
- all Items in the current SO will be marked as is Dropship on the Current Availability form
- after SO saving, related PO will be placed in Purchase Order Request -> Dropship Request
- if at least one Item from the SO unchecked as is Dropship on the Current Availability form, then on SO edit form checkbox Is Dropship should be unchecked automatically
