For importing images. Add features.

[Sebanisu]

• add abilities to customize the tile settings. You base on an existing tile but you could still change the values in that tile except the X,Y,Source X, Source Y, and Texture Page. Those values are computed.
• Ability to change where the imported image is drawn
• Prepend, Append. Place before or after tile number. If the tiles were listed like photoshop layers you could then just reorder things as you see fit.
• Make rendering of added tiles blend more correctly with the existing tiles. Currently they are just drawn on top of existing tiles.