Filter out split geometries with too few buildings

[spwoodcock]

Describe the bug

• The splitting algorithm may produce a random split geometry that contains no features (see the tiny blue polygon):

• This shouldn't happen often, but is possible.
• In order to avoid, we should filter out any final polygons that have areas smaller than a certain size, perhaps 10m2?

To Reproduce

• AOI GeoJSON:

{"type":"FeatureCollection","features":[{"type":"Feature","properties":{},"geometry":{"coordinates":[[[85.29998911024427,27.714008043780694],[85.29998911024427,27.710892349952076],[85.30478315714117,27.710892349952076],[85.30478315714117,27.714008043780694],[85.29998911024427,27.714008043780694]]],"type":"Polygon"}}]}

• Data extract attached as a .txt file to get around upload restrictions. Rename to .geojson:

kathmandu_extract.txt

• Use the splitting algorithm set to 100 buildings average.

Expected behavior

• Geometries like that are clearly an artifact that should be removed.

[spwoodcock]

This should be fixed by #53

If we need an actual threshhold param, we can revisit this if needed.

[Sujanadh]

Actually I think we don't care about area if it has sufficient features in it ( for example each task with around 40 features lets say if user wants to split by num_buildings=40), so we need to determine threshold based on the number of features per task maybe (-0.5x to 0.5x => 20-40-60 not less than 20 or not greater than 60)