Report missing required components

[jcornaz]

As a User, I wan't to get clear and quick feedback when I make a mistake, so that I avoid spending time guessing/debuging in order to make my game work.

For example the Body component needs the entity to also have a GlobalTransoform. And a Velocity works only on dynamic bodies.

When a required components is missing it can be considered a programming mistake of the user of this library, and Heron should at least report the situation, so the user is aware of it.