Tcod-ecs

Added

- `Entity.relation_components` now has `MutableMapping` functionality.
- You can now set the value of `Entity.relation_components[component_key] = {target: component}`.
- Added the `Entity.clear` method which effectively deletes an entity by removing its components/tags/relations.
This does not delete relations targeting the cleared entity.

Added

- Now supports giving a query to another relation query, allowing conditional and chained relation queries. https://github.com/HexDecimal/python-tcod-ecs/issues/1

Changed

- The type returned by `World.Q` has been renamed from `tcod.ecs.Query` to `tcod.ecs.query.WorldQuery`.
- Serialization format updated.

Performance

- Added a simple query cache.
A query is automatically cached until any of the components/tags/relations it depends on have changed.

Changed

- Serialization format updated, older versions will not be able to unpickle this version.
- Reduced the size of the pickled World.

Fixed

- Missing components in `Entity.components` now returns the missing key in the KeyError exception instead of the entity.
- Backwards relations for querying were not cleared on relation deletions.

Added

- `Entity.components` now supports the `|=` assignment operator.

Added

- `Entity.tags` now supports the `|=` and `-=` assignment operators.