Added Catmull-Rom spline type which interpolates through the control nod...

...es

I found that it is very difficult to control current the curve with current splinepath class because slightly change of one node changes all curve. So, here is Catmull-Rom spline which interpolates through control nodes and position change of one node changes curve only locally(4 nodes). Note it needs 4 nodes minimum to actually work.
Preview camera flying through this spline.
http://gfycat.com/TediousHeartyEnglishsetter