Added custom scattering factors and other updates
New features:
- added custom scattering factors
- add magnetic scattering factors for heavy elements
- added additional plot and display commands
What's Changed
- Supercell scale fix by @DanPorter in #31
- Add 3D intensity plot by @DanPorter in #35
- 32 feature request custom atom form factors by @DanPorter in #34
Full Changelog: v3.3.3...v3.4