Updated demo and removed call to 'mathutils.geometry'.

[costika1234]

I would ideally like to get rid of the mathutils dependency at some point, so I've just replaced the call to mathutils.geometry.intersect_point_line with a simple Python function called _intersect_point_line. I've also updated the demo with a new floor plan to better test the program and added a quick benchmark function. There is virtually no difference between the 2 implementations (on my machine it took about 10 seconds in each case).