Edit polynom to polynomial in all files. File polynom.h edited to polynomial.h and bezier_polynom_conversion.h to bezier_polynomial_conversion.h

Modified constructor (set time directly in constructor) / add getters for control points and their time corresponding

Edit doc of cubic_spline, exact_cubic, quintic_spline, spline_deriv_constraint. Modify name of variables min and max to t_min and t_max.

Fix evaluation of bezier of degree 0 added, Edit doc on bezier_curve, Edit assert_allclose to assertTrue in test.py

change namespace spline to curve in include folder, rename folder spline to curve, change in the CmakeList.txt