Implement AFMs (all geom) and 3D FMs
- implement 3D confined FM samples (without dipolar interaction)
- implement AFM samples (constructor, mode movie, show sample, show_mode, eigensolver, minimizer, etc)
- implement AFM interactions (including uniform DMI)
- reading and writing of AFM profiles
- move operators into their own packages per interaction (e.g. exchange FM and AFM together)
- Fix return of the magnetization in the relax function when relaxation fails.
- smaller fixes