Create ground truth montage for testing

[dzenanz]

1. pass in an arbitrary image
2. which is then to be cut into a montage with small variation in positions (including fractional pixels)
3. ideally also add different shading and/or noise to each tile to simulate real-world conditions
4. write that to disk so it can be later compared with Fiji
5. run the montage class and assess errors
6. run the stitching class and compare it with original image
7. invoke this test with multiple images and parameter combinations (montage size, positioning variation etc)

This will allow testing peak interpolation methods, as well as build-up of registration errors over a montage.