Bravais

Added

- `Sites` class used from `spatial-sites` package for internally storing lattice sites.

Changed

- To be consistent with the new `Sites` class, the `BravaisLattice` attribute `row_or_column` has changed to `vector_direction`, and it now accepts "col" in addition to "column".

Fixed

- Cubic lattices can now have the body-centred (I) centring type.

Changed

- Added an American-spelt version of the BravaisLattice attribute `centring_type`: `centering_type`.
- Lattice parameters `a`, `b`, `c`, `alpha`/`α`, `beta`/`β` and `gamma`/`γ`, `lattice_system` and `centring_type`/`centering_type` are now properties and therefore cannot be modified after instantiation.

Fixed

- `row_or_column` attribute is now respected by `lattice_sites` and `lattice_sites_frac` attributes.
- Deprecation warning from `pyyaml` has been resolved.

Changed

- This is the initial "complete" version; PyPI "development status" has been changed from "3 - Alpha" to "4 - Beta".