Interface changes and refactoring.

Interface changes:
- Only ofxReprojection deals with window segments for mainWindow and
  projector.
- ofxReprojectionCalibration is used through draw functions
  drawStatusScreen and drawChessboard, both accepting positions/rects as
arguments, as usual in openFrameworks.
- ofxReprojectionRenderer has drawImage functions for inputting 2D
  images, and setDrawArea for specifying where in the window they should
be drawn.