Huge refactoring + many new tools (pen, image, zones) and features (choice between glyph or bitmap gen)

Moving everything for a classic MVC.
Adding an "image" mode to draw big image instead of font glyphs.

Adding new tools :
- Pencil (as before)
- Image : allows to load any image to draw it on the grid
- Zone : allows to define areas on the image. The area's coordinates
will then be generated above the image's data. This is meant to make
image injection a bit easier.

Adding possibility to drag the grid with SPACE+mouse or middle button.