Quick ASE VibData -> Euphonic ForceConstants Interface

[rebeccafair]

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

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