Added show commands method, etc.
Made showAll() and showCommands() methods return a String instead of...

...void so that the help message is formated solely in the Game class.
Will probably rename showAll() to getCommandList() and make it static in
the CommandWords class (Don't know what Java textbook doesn't suggest
that, maybe I should keep reading.)
Renamed showAll() to getCommandStringList() and made static, removed...

...Parser.showCommands() method. As long as validCommands[] in
CommentWords class is initialized right away, this method should be fine
by being static.
Added Item class, and Item list as field in Room class.
Switched weight measurement to kilos, using doubles, so I can add
smaller items
Added items to certain Rooms.