Level creation, Tile and Object HashMaps, sprites

Switched wallsprites from individual spritesheets to packaged
spritesheet, fixing whitespace issues.
Incorporated chair sprites and the solid tile sprites.
Made IO error messages include strings saying where the error was (not
necessary but nice).
Levels based on images now, imported with loadLevelTiles() and
loadLevelObjects().
Tiles rendered a spot higher than they should be to compensate a gap
between them and the walls.
Tiles and Objects all have number and rgb constants. These are set in
their constructors and stored in class hashmaps. This allows Level to
call the respective classes to know which tile to render based on its
integer level arrays.
Created a small example level
Created color-to-sprite maps for use in level-making.