Update dataset and course to use geo aggregations.

[simonprickett]

This course should be updated to use geo aggregations (find stuff near somewhere). This will require an update to the data set (maybe add some library locations) and should include both radius and the new polygon geo functionality when that's released.

These should be added as text segments rather than new videos. We can also point to any video / live stream / demo repos that we put out as well.