CPS 108 - Fall '10
11/15/2010

OVERLAY API
AUTHORS: Andrew Brown, Se-Gil Feldsott, Justin Goldsmith

To use the Overlay classes, the user should make each variable he wishes to display be of type Stat<T> or StatInt. The user should then pass, 
that variable to the constructor of the Overlay, and the Overlay class will use that stat to keep updating the score (etc).

CLASSES:

-OverlayBar-
This overlay displays a value as a gauge that increases and decreases
according to the current value.  It requires a Stat<Integer>, and the size of the bar grows and shrinks in real time.

-OverlayHelp-
This class contains helper methods that gathers information about text size.
This is NOT an Actor class.

-OverlayIcon-
This overlay displays a number of icons according to value being kept track
of.  The image used and the Stat<Integer> or StatInt that determines how the value
increases and decreases are passed in by the user upon instantiation of this
class.  This class extends OverlayString.

-OverlayStat-
This overlay displays a statistic or integer value.  It takes in a
Stat<T> or StatInt and displays the value based on the output
of the getStat() method.  This class extends OverlayString.

-OverlayStatImage-
This overlay statically shows an Greenfoot image.  It is used by the
OverlayIcon class to display each icon that is currently showing on the
screen.

-OverlayString-
This overlay is the base class for displaying a String with the option of
specifying a font and/or color.  This class is extended by OverlayIcon and
OverlayStat.

-OverlayManager-
This convenience class lets the user easily group Overlays and manipulate them all at once.
It can remove all the overlays, move them all a certain distance, or position them all relative to the same point.

-OverlayPanel-
This convenience class lets the user easily create a bar of Overlays across the top or bottom of the screen.

-Stat<T>-
This class is the variable type for all statistics.

-StatInt-
This is a convenience class that uses an int instead of the equivalent Stat<Integer>.

-StatKeeper-
This interface uses its getStat() method to return a generic value.