Quick ASE VibData -> Euphonic ForceConstants Interface

[rebeccafair]

Initially create separate repo for quick implementation of ASE VibrationsData -> Euphonic ForceConstants

• [x] Create initial repo: https://github.com/pace-neutrons/ase_euphonic
• [x] Proof of concept: vibrational DOS
• [ ] Validate eigenvectors:
  • [ ] Read ASE eigenvectors into Euphonic
  • [ ] Compare structure factors for ASE-calculated and Euphonic-calculated eigenvectors