Feature nndata genereator
This branch adds:
- Data Generator for realizable set and monomials with degree <= 1.
- Monomial Basis for moment solver (addition to shperical harmonics)
- Unit tests for monomial basis
- Validation tests for monomial MN solver
- Some code restructuring
- Reduced number of (unneccessary) assertions in unit tests
- Linesource test case now with MN Monomial solver