Extend options are currently stored per curve. This was not clearly communicated to the user and they expected this to be a setting per CurveMapping. This change will move the option from `Curve` to `CurveMapping`. In order to support this the API had to be changed. BPY: CurveMap.evaluate is also moved to CurveMapping.evaluate what breaks Python API. Cycles has been updated but other add-ons have not. After release of 2.81 we can merge this to master and adapt the add-ons. Reviewed By: campbellbarton Differential Revision: https://developer.blender.org/D6169