edge_size should be a parameter when calculating resolution of PointClouds

[j9ac9k]

Issue created from this comment

#74 (comment)

To calculate the PointCloud.native_resolution we take the units_factor and multiply it by the pdal pipeline metadata["filters.hexbin"]["avg_pt_spacing"]. The hexbin filter as it stands is pdal.Filter.hexbin(edge_size=25, threshold=1). The edge_size parameter for this filter should be a parameter that users can configure if they want, as it is unlikely to be suitable for all lidar data collections.