Derivative operators for triangular mesh - deg 1

[Didou09]

1/ Get familiar with how things are done for rectangular meshes
Files to take inspiration from rectangular meshes:

• _class02_bsplines_rect.py
• _class02_operators.py
• _utils_bsplines_operators.py

2/ Start implementing basics for triangular meshes in a similar way to rectangular meshes
Recommended pathway:

Create a _utils_bsplines_operators_tri.py for triangular meshes
then update _class02_bsplines_tri.py

Activate

3/ Write tests to:

• automatically test that the implementation is correct
• have an easy way to run a test during development

In , tests/test_01_Mesh2D.py write (the code will live in tests/test_input.py)