rename Python module from 'raytracer' to 'pyrit'
improve Python binding:
  - new objects: Container, Octree, KdTree, Shape,
    Pixmap, Sampler, DefaultSampler
  - all shapes are now subclasses of Shape
  - clean, remove redundant Getattr's
  - Raytracer render method now just wraps C++ method
    without doing any additional work
adjust all demos for changes in Python binding, remove PIL dependency
add demo_PIL.py as a example of pyrit + PIL usage
render_nff.py now either loads file given as a argument
    or reads input from stdin otherwise
fix bug in pixmap float to char conversion
Import('pymodule')
env = Environment()
env.Append(BUILDERS = {'Copy':Builder(action=Copy('$TARGET','$SOURCE'), single_source=True)})
files = [
	'boxes.py', 'buddha.py', 'bunny.py', 'car.py', 'dragon.py',
	'spheres_ao.py', 'spheres_glass.py', 'spheres_shadow.py',
	'triangles_monkey.py', 'triangles_sphere.py',
	'objreader.py', 'plyreader.py', 'lworeader.py',
	'vector.py', 'render_nff.py', 'demo_PIL.py']
l = []
for file in files:
	l.append( env.Copy('#build/demos/'+file, file) )
import os
l.append( env.Copy('#build/demos/'+str(pymodule[0]).split(os.sep)[-1], str(pymodule[0])) )
env.Alias('python-demos', l)