Reformat Node + Sampler + Filters

Added:
Sampler Class:
A utility class that allows an image plug to have it's pixel values sampled.

Refomat Node:
Currently a simple node that efficiently scales an image input to an output format using a chosen image filter.

Filter Class and the following filters:
Bilinear
Box
Bspline
CatmullRom
Cubic
Hermite
Mitchell
Sinc

Todo: There is an outstanding bug I am looking into where the reformat won't output to the default format. 

Luke