Transaction window price

Fixed the transaction window price bug (issue #59).  The TransactionStartEvent now records what the rum price is at the port where the transaction is happening, and when the human game view handles TransactionStartEvents it stores this price in a new tc_rum_price variable.  This variable is referenced, instead of the original incorrect price calculation, for display in the transaction window.

No more "Price: 4326645743" or "Price: -1"!