Add storeroom to vendor configuration

Vendors now have a storeroom parameter.  If the vendor has a
storeroom, it will use the contents of the room instead of its
inventory for the items to be sold.

This was done primarily so consigment shops could specify a house room
as a storeroom so that objects could be automatically saved.
Consignment added to vendor

Two commands, consign and unconsign were added to the vendor.  A
consignor and consign_price were added to the obj_data structure.
same_obj() was modified so that items with different consignors are
considered different.
Improve logging of consignment activities
Merge pull request #253 from dlowe-net/feature-vendor-consignment

Feature vendor consignment