Added the get with default method to the attribute manager
#7: Added code to the size getter method in LayoutUtils so that the
absolute size attributes (width and length) override the min and max
ones and the size guides.
#7: Removed the max-inf attribute and added the fill-container
attribute.  I think this one makes more sense.
#7: Cleaned up FlowLayout a little.  Fleshed out what I want to do in
the layout method.