Map editor now displays sprites

General
-Updated some references to old art to new art
-Updated spike.png map editor ui icon to new art

SwingButton.java
-fixed typo "Failed to load image at +"

MapEditor.java
-added array of images for game elements
-added image shadows that preview adding elements to the level
-added functionality to create a string representing a level
-added ability to scroll horizontally infinitely

Toolbar.java
-fixed currentTool to never be null (previous behavior: initialized to null)
-fixed repainting so that changing tools causes MapEditor to repaint
(previous behavior: MapEditor did not change to the new sprite)