Fix densification functions

[pjhartzell]

Related Issue(s):

• Closes densify_by_distance not retaining original polygon vertices #411

Description:

• Replaces the densify_by_distance algorithm to retain the original polygon vertices (which fixes densify_by_distance not retaining original polygon vertices #411 ) and to only add new points on polygon segments longer than the distance argument. Example image (same as shown in the issue) showing the now correctly densified polygon:

• Fixes a problem with densify_by_factor where the last/closing vertex was not included in the returned densified point list.
• Makes the footprint method return counter-clockwise polygons to align with the GeoJSON specification. Updates tests to use counter-clockwise polygons. I found that Shapely's convex_hull and simplify methods return clockwise polygons, so these methods are now wrapped in an Shapely's orient function to enforce counter-clockwise polygons.

PR checklist:

• Code is formatted (run scripts/format).
• Code lints properly (run scripts/lint).
• Tests pass (run scripts/test).
• Documentation has been updated to reflect changes, if applicable.
• Changes are added to the CHANGELOG.