Code in the `_line()` of the sibling Bezier edge types was either extremely similar or identical.
The Bezier drawing code has been consolidated in a single method in the parent class.
* element characteristic changes
* assume edge color inheritance is correct before choosing
* Adjust nodes’ chosen’s boolean -> bool
* Need to get user-reset size
* make example edges thicker for more noticeable shadow
* preemptive ES6 fix (see #2500/#2501)
* documentation for the feature that was previously overwritten