Added new ImageSprite

- Created the ImageSprite class.
- Renamed BackgroundPane to ImageComponent.
- Moved ImageComponent to yuuki.graphic.
- Updated GraphicalInterface to reflect changes.
Added tile loading and some basic tiles
Added the image property to Tile
Changed type of Tile.image back to String
Changed WorldViewer data types to Image
Added custom painting to WorldViewer
Added overworld image reference to Character
Added temporary sprite art
Added portal definitions file
Added portal image file
Added portals to world loading sequence
Cleaned source code
Made non-existing files cause an exception
Moved the portal pic to the correct dir
Moved world loading off of the EDT
Fixed error in data def file
Made graphics display to close #43
Merge remote-tracking branch 'origin/feature-graphic-world' into development