Colour Table

Coloured rendering is now partially complete.

This is the colour table that maps voxel value to a colour and opacity. What I plan on implementing next is a small preview of slices of the volume, so it is easy to visualise how the colours will map onto the volume without having to actually render it.

After this, the next major feature is simple lighting, which hopefully won't take too long to do, and then to optimise the ray casting technique.