Optimize and cleanup operators2d
Created originally on Bitbucket by avmo (Ashwin Vishnu)
Was already merged in Bitbucket before import, marked as merged by the import user
Update: no betaplane solver in this PR.
- Add pending deprecation warnings for oper.laplacian2_fft and oper.invlaplacian2_fft methods. More generic methods instead. Also use faster Pythranized laplacian_fft and invlaplacian_fft functions for many methods in operators2d
- Change laplacian2_fft and invlaplacian2_fft in plate2d solver
- Operators 2d: rm unused attributes Kappa2 and f_over_c2Kappa2, add more useful Kappa2_not0
- Improved fluidsim_load magic
phys_fields.interactas a separate method.