Figure out how to align and stack layers

[zacharylazzara]

Once the DataLoader and tile stitching are finished, we can begin working on aligning layers. This will depend on the image stitching class (which itself will depend on the DataLoader class), and will take two X,Y,Z tuples as arguments, then return the aligned and stacked layers.

The ultimate goal is to produce a 3D voxel map, but we also need to ensure the whole thing can fit into memory. Since we won't be able to fit everything into memory at once, the scanning systems will need to produce a 3D coordinate space that they're interested in, which will be sent to this class. This class will then return the requested 3D data, using previous classes to build that data from the images on the fly, and discarding the data once its no longer directly in use.