Add HaarLoader and ImageConverter

This adds a HaarLoader class which will load a haar file based on
a predefined name.  This will cache the loaded haars within the
thread, so they will not be constantly loaded.  Haar cascades can
be loaded from files and cached to the thread using an optional
cache name.

This also adds basic ImageConverter class which will convert images
from RGB to grayscale.  Later this will be used for other imaging
related tasks.

These, like many things which will be committed tonight, need some
tests to back them up.