Crate all_is_cubes_ui

User interface framework and screens for all_is_cubes.

This crate does not provide any platform bindings, but contains components for the platform-independent components of the complete interactive game application. If you create a Session, it will manage the Universe, the UI, and user input; you need to provide:

• A renderer of Spaces (both the game world and the UI); possibly using all-is-cubes-gpu, the software raytracer, or your own code.
• Delivery of input events to Session::input_processor.
• Various hooks into IO and windowing functionality.

TODO: Modules of this crate need a review of their organization.

Modules

• apps
  Components for “apps”, or game clients: user interface and top-level state.
• logo
  Drawing the All is Cubes logo.
• notification
  Types used to create notifications displayed to the user.
• vui
  Voxel User Interface framework.