checkcouldactivatePO should be expanded

[Tiffany Little]

Right now there are several criteria that are checked before a purchase order is allowed to be activated:

1. Whether the sum of amounts charged to a particular fund exceeds the stop percentage (exceeding warning percentage is still allowable with a notice)
2. That all line items have quantities
3. That all line item details have funds
4. That all line items have prices

As far as the "Activate without loading items" check, I think that's fine. However, activating an order that will be creating copies has some other constraints that aren't currently checked for, but will cause the activation to fail. Ones I have noticed:

1. LID does not have an owning library
2. LID does not have a shelving location (see: #1440944)
3. Line item is not linked to a bib record (i.e. 'link to catalog')

If possible, it should also check that the bib record a particular line item is linked to is deleted or not, but I can deal with it if it doesn't check this. This would be dealt with by bug #1634244 which currently has a pullrequest (but I haven't tested it yet).

So the checkcouldactivatePO for the 'Activate' button should be a more rigorous check than the 'Activate without loading items' button.

ETA: And the warning notice if it fails any of those checks should specify a list of the line item IDs which failed the check, so that users can go through the list and fix them.