Extend options are currently stored per curve. This was not clearly
communicated to the user and they expected this to be a setting per
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