Camera commit.

Changelog:
 1. Camera
  - Translation (arrow keys)
  - Zoom in/out (mouse wheel)
  - Rotation (middle mouse button + mouse wheel)
 2. Selector
  - Added support to camera

Issues and Bugs:
 - Scaling is not centered nor follows mouse.
 - Rotation, although centered, does not yet have support to selector.

TODO:
 - Scale must follow mouse.
 - Rotation must be supported by Selector.