#9 Change SellCommons() function to take diff trade sizes

[Owen Pauling]

It would be good if the SellCommons() function took
two parameters: one for the number of objects to
sell, and another for the number of tickets to
receive for them. As well as being able to trade
32/1, 16/1, 8/1 cards, etc, you'd also then be able
to sell stuff like boosters for 4 tix, or 2 rares for 3
tix, etc.

This would also prove useful later if we write code
for transfering the contents of one account's binder
to another. The bot would be able to sell 32 objects
for 0 tickets, and then this could be repeated until
everything has been transferred.