text: Title: [FEA] tree layouts should support a planar layout mode
  Body: **Is your feature request related to a problem? Please describe.**
  
  When plotting tree data, edges sometimes intersect. Ex:
  
  ```
  g = (g
       .get_degrees()
       .tree_layout(
          level_sort_values_by='degree',
          level_sort_values_by_ascending=False,
          level_align='center',
          vertical=True,
          ascending=True)
       .settings(url_params={'bg': '%23' + '000000', 'edgeCurvature': 0.05,'edgeInfluence': 1.5,'pointSize' : 0.5})
       .layout_settings(play=0, locked_x=True)
      )
      return g.plot(render = False,memoize = False)
  ```
  
  On planar graphs (ex: trees), this should be avoidable
  
  **Describe the solution you'd like**
  
  The default should be something like sort-by-parent-position (`level_sort_mode='parent'`?), which can be used if `level_sort_values_by` is not set
  
  **Describe alternatives you've considered**
  
  * radial versions of the same
  * implement / embed reingold tilford (tidier)  (ex: https://hci.stanford.edu/courses/cs448b/f09/lectures/CS448B-20091021-GraphsAndTrees.pdf)
  
  