Fix coordinate saving

[rwood-97]

Summary

This PR ensures that coordinates of the downloaded maps are saved correctly.

When downloading tiles, the coordinates of the tile at (1,1) correspond to the bottom left corner of the tile. This is the same as the upper right corner of tile (0,0).

If tile (3,3) makes up the upper right corner of the map image we have downloaded, then the coordinate of the upper right corner of the map image is not the coordinate (3,3) but actually (4,4).
This needed updating in the code as the coordinates that were previously saved were off by one tile index.

Describe your changes

Coordinates of NE corner of the map is now tile index +1 .

Checklist before assigning a reviewer (update as needed)

• Self-review code
• Ensure submission passes current tests
• Add tests

Reviewer checklist

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• Everything looks ok?