Working on #49: part of the reason items didn't appear to be picked up was that
the GUI was clearing the list of items too frequently while reading it from the
character file (my fault), so only one item was displayed. Also fixed some
things about member visibility in the GUI.
Fixed #49: the main problem was that several places were calling the function for using an inventory item (perform-item-transaction) when they should have called some other functions for general item handling. Some functions were renamed for clarity.