Remove data directory created inside project by running locally
Move feq() and is_zero() to mathutil since they are general math functions not related to geometry
Only check the region of the map that couple possibly be changed by the sensor update to reduce (drammatically) the number of cells to check. Update the cell value proportionally to the amount of the cell covered by the sensor update (using the number of intersecting corners as a proxy for the overlapping area). Closes gh-21