Define rendering resources

[martinjonsson01]

Reason

Use resources in the renderer instead of hardcoded constants.

Requirements

• There is a UpdateRate resource which contains an instance of gfx::time::UpdateRate
• There is a MainThreadSender resource which contains an instance of Sender<gfx::engine::MainMessage>
• There is a RenderDataSender resource which contains an instance of RingSender<gfx-plugin::rendering::RenderData>
• Extract tick_rate_system into a function-system (not a closure) inside the gfx-plugin::rendering module
• Remove rendering_system_wrapper and have the gfx-plugin::rendering::rendering_system take RenderDataSender as a resource instead
• Update example code (rendered-ecs.rs) to use delta time
• Update case studies to use delta time

Dependencies

• System resource access #68
• Rendering system #61