spline projection operators
- run test_conga_projectors.py script and see what it does
- see in details how the 'ps' Projection is constructed (compare definition in paper and code)
- visualize v and Pv for different functions v in the broken space, and different grids
- use two bases for the broken Spline spaces:
- one corresponding to open knot vectors on each patch (in principle this one is already implemented)
- and another one corresponding to regular knot vectors (with knots outside the patches rather than repeated on patch boundaries)