This will make a lot of simpler actions and scorers much less boilerplatey

This allows for easier continuous actions, and I think is more intuitive

Fixes: https://github.com/zkat/big-brain/issues/29

Fixes: #26

* add test for steps and fixes
* define system ordering

BREAKING CHANGE: This is a significant licensing change. Please review.

Without this change, this plugin pulls in dependencies for Bevy features I don't need when used as a plugin (E.g. the audio feature is enabled even though neither I nor this plugin require it.) All features are re-enabled in `[dev-dependencies]` so examples are unconstrained.

* Added EvaluatingScorer

* fixed doc issue

Co-authored-by: doomy <2640792-_doomy@users.noreply.gitlab.com>