[FEATURE] calculate structural data from lines and DTM

[lachlangrose]

Input: Basal contacts or faults, DTM
Expected knowledge: estimate of planar dips (with large uncertainty!)

Originally posted by @markjessell in Loop3D/plugin_loopstructural#28 (comment)

[rabii-chaarani]

will continue to work on dip calculator class: https://github.com/Loop3D/map2loop/tree/dip_calculator