Create a separate plugin for handling all view rendering

[MeoMix]

With the introduction of model/view separation, it seems important to more clearly define the boundaries. The most extreme way of doing this would be to create entirely separate crates and I think that idea has long-term merit, but, for now, the next most aggressive decoupling is to introduce separate Plugins (https://bevyengine.org/learn/book/getting-started/plugins/)

The idea here is to move all UI rendering logic into a "View/Render" plugin and to keep all model/simulation logic outside of this plugin. This will allow for better enforcement of pub/priv modifiers and help ensure that, in the future, if we move the simulation logic to a server, that it's trivial to do so.