Add 2dsphere index support

[josx]

it seems to be missing 2dsphere index support, please add it.
I can help if needed

[derwaldgeist]

Setting index: '2dsphere' works. Just confirmed it with Studio 3T.
If you've already defined an index on the key, just might have to remove it first (index: false) and then re-set it using 2dsphere.