Add nice geo-serialization

Introduces a new requirement, but gives us location serializations like:

    "location": {
        "type": "Point",
        "coordinates": [
            -3.55378735554,
            52.4424721842
        ]
    }

instead of:

    "location": "POINT (-3.5537873555399999 52.4424721841999997)",

Nice.
Merge branch 'api' of github.com:jimr/openwater into api