Pre-release 1.0.0 - Merge Flare++ & Use yaml for training & On-the-fly with Lammps

What's Changed

This version includes major changes in the code structure and interfaces (More details are in the pull request #303)

• Rearrange modules
• Clean up unused code
• Merge flare++ into flare
• Use yaml file for training (same command, different config files for on-the-fly training, offline training, restarting, combine multiple dataset/models)

  flare-otf config.yaml

  (see flare/examples for the format and parameters for yaml)
• Add on-the-fly training by LAMMPS and offline training (fake MD/DFT)

Backward compatibility notices

• freeze_hyps is replaced by train_hyps, where an interval (a, b) is specified, and the hyps will only be trained when the GP model has number of training data in this interval

Release notes (auto-generated)

• Subtree for flare_pp repo by @YuuuXie in #304
  Full Changelog: 0.2.4...1.0.0