don't bring back onchange of picking type

This is due to purchase-workflow#66 that
converts that onchnage to new API (this in turn was to be consistent
with purchase_delivery_address where this onchange was first defined).

This fixes an incompatibility with purchase-workflow#66 that gives a
crash when changing the picking type on a purchase order.
bring back other view changes upstream

These other changes were made in purchase-workflow#66.
Merge pull request #83 from lepistone/fix-onchange-picking-type

don't bring back onchange of picking type