[Fixed] Multiple vendor issues

[Fixed] Selling an item from stockroom no longer counts that item's size
twice in the item count check
[Fixed] Retrieving an item from a vendor now considers the item's size
when checking inventory space
[Fixed] Relisting a sale from stockroom to always place the sale back
onto the vendor it was already on
[Fixed] A player can no longer place items for sale on vendors if they
have more vendors than their maximum