Ft higher order derivatives

[jzwar]

Higher order derivatives and bugfix for Fit functions

• solves Weights should be "normalizable" splinepy#299
• you can now compute the close form derivative for Beziers more easily to higher orders directly without copies

Check list

Test documentation (delete if not applicable)

• Build Debug
• Build Release Mode
• Executed Tests
• Build Tests
• Executed Examples
• Added new unit test for new feature

Documentation of changes and theory

• I have updated the relevant documentations, as far as necessary.

Style guide compliance

• Edited C++ files formatted with clang-format (10.x.x+)

[j042]

Nice and natural extension of DerivativeWRTParametricDimension, thanks!

[j042]

Nice, thank you!