Support knot insertion up to C^-1

[j042]

Overview

Adds support for C^-1. Changes of this PR also fixes #215. In cpp, to extract cp ids for bezier patches, you now need multiplicity informations - This is available from KnotVector. For #297, we can also wrap this.

Addressed issues

• C^-1 spline creation through knot insertion was impossible

• 215

Showcase

A short / one-liner example to highlight the (new) feature

# bspline with no knots at 1.5
assert all(bspline.insert_knots(0, [1.5] * (degree + 1)))

Known ToDos

• elevate degrees with c^-1 splines fails

Checklists

• [ ] Documentations are up-to-date.
• [ ] Added example(s)
• [ ] Added test(s)

[j042]

test freezes @ windows-debug build

[jzwar]

LGTM, thanks for handling this. Please fix tests before merging