Adds slicing and striding for the 3D volume visualizer.
Adds slicing and striding for the 3D volume visualizer.

This commit adds a simple method for slicing and striding a 3D bh_array
when using the volume viewer.

Dependencies for the visualizer is:

freeglut3-dev
libgl-dev

and possibly also the mesa dev drivers

bh107/bohrium,madsbk/bohrium,madsbk/bohrium,bh107/bohrium,bh107/bohrium,bh107/bohrium,madsbk/bohrium,madsbk/bohrium