Completed base curve wrapping
Completed base curve wrapping

Modification to interface:

 - new methods `intersect`, `intersect_ISO`, `intersect_SAE`, `closestPoint`, `findST`
 - different return value in `closestPoint_ISO`, `closestPoint_SAE`, `findST_ISO`,`findST_SAE`
- documentation for all methods in base curve class
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