Refactor edges normal_vector and direction_vector methods

[GabrielJMS]

• I'm submitting a ...

  • bug report
  • feature request

• What is the current behavior?

The edges objects possess the methods normal_vector(), unit_normal_vector(), direction_vector(), and unit_direction_vector(). It is possible to simplify these four methods into just two methods: tangent() and normal(). These two new methods would accept the same parameters as the previously mentioned methods, with an additional optional parameter to specify whether the result should be normalized.

• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem Avoid reference to other packages

• What is the expected behavior?

• What is the motivation / use case for changing the behavior?

• Simplify and mutualize

• Possible fixes

• Please tell us about your environment:

  • branch:
  • commit:
  • python version: