Harden up contracts between Edges core and Renderers

[richard-jones]

Currently the core, components and renderers are loosely coupled, making it difficult to be sure you can switch them around as you would like. Renderers are essentially dependent on their Component to be the right shape, which means it can be difficult to use Renderers on multiple components, and vice versa. We should architect a better way of defining the contract between the edges core and the renderers so that there is more portability.