Added a pure psydac version for the mhd operators
- No Struphy point sets needed, removed struphy 1d projectors from mhd ops.
- New function "get_span_and_basis" in mhd_ops_pure_psydac.
- Use psydac find_span and basis_funs_all_ders to compute basis function values at point sets.
- Much slimmer code in prepare_projection_of_basis, no Vcomp, Wcomp name strings needed.
- Kernel slightly adapted to account for distributed point sets of the projectors.
- Added parallel capability to psydac mhd_ops.
- Added small-letter projectors from set_projectors("general") to unit test. They give a flattened output, in contrast to the usual ones.
- Update ci because of new (more complicated) psydac installation.