Solved bug: multiple items deleting, added more monsters

added two more monsters types, made creature constructor pull the icon
from it's class definition.

solved bug of multiple items being deleted by removing extra occurance
of splice();

moved addTile() for better grouping
Implemented Floor() obj, changed other functions to reflect refinement

added constructor Floor()

floor objects are stored in an array called world[]
all game driving functions were changed to reflect the new way that the
world data is stored.

many functions belonging to the global scope or to Tile() are now
methods of Floor()

methods for generating different kinds of floor maps should go in
Floor()

several small issues related to the new implementation were solved.