AWS 2-6: Add Hybrid Tiling Endpoint

[rajadain]

Once the research is done for #10, implement the hybrid tiling endpoint and demonstrate its use.

This endpoint should:

• Be configurable with an S3 bucket for cached entries
• For every request, check if there is an image in S3. If so, it should serve it.
• If not, it should generate it, then save to S3, then serve it.
• If it cannot be generated, it should return a 500
• Return a 404 if the specified layer is not found