0.0.5G - ELevel and add_filler changes.

+ Level Editor now has a special ELevel version of Level.
~ ELevel now handles the grid itself. Recommended that each Level
handles their own loading of a grid.

~ add_filler has been cleaned up nicely, and is now an x/y loop.

- Left and upward boundary addition has been broken again. Implement it
for the new ELevel and Grid.