Ase-extension

Changes

- `LogFermiWallPotential` is renamed to `LogFermiSphericalWallPotential`
- Added base class for bias potential: `ase_extensionn.constraints.BiasPotential`
- Internal API changed (See commits)

Features added

- `ase_extension.neighborlist.neighbor_list`: A drop-in replacement of `ase.neighborlist.neighbor_list`, but much faster and supports multithreading by `rayon`

Features added

- `ase_extension.geometry.RMSD`: Compute minimum rmsd (and its gradient) between two `Atoms`

Features

- Log-Fermi spherical wall potential: `aseext.constraints.LogFermiWallPotential`