* Now Application::build() takes a Context as a paramater instead
  of Config
* Now RenderingProcessor::new() takes scene_name and context as
  parameters and calls context.renderer.add_scene()
* Add num_lights method to context::renderer::Renderer
* Add num_fragments method to context::renderer::Renderer
* Note: if you delete a Component associated Fragment or Light won't
  be deleted from the frame.

* Now Fragments and Ligts corresponding to deleted components
  are deleted from the frame

* Add RendererConfig config struct to the processors::rendering mod,
  it contains the pipeline (Forward or Deferred), the shading (Flat or
  Shaded), and the clear color.
* Now RenderingProcessor::new takes RendererConfig as a parameter
  and creates and sets a pipeline according to this config
* Add ACTIVE_SCENE_NAME and ACTIVE_CAMERA_NAME constants to
  processors::rendering mod
* Now RenderingProcessor::new doesn't take scene_name as a parameter
  instead it adds the default scene with name = ACTIVE_SCENE_NAME to
  the frame

* Add translation, rotation_axis, rotation_angle, and scale fields to
  Renderable component

* Add amethyst::engine::Config containing ContextConfig and
  RendererConfig
* Rename amethyst_context::Config to amethyst_context::ContextConfig

* Remove State::update impl from window.rs example
* Remove State::update impl from sphere.rs example

* Don't register rendering processor Components in
  ApplicationBuilder::new.

* Now amethyst::processor::Camera::new takes Projection as an argument
  instead of fov, aspect, near, and far arguments.
* Add amethyst::renderer::Camera::orthographic function, which returns
  an orthographic projection matrix.

* Add more doc comments to processors::rendering mod

* Panic if renderer_config.pipeline or renderer_config.shading field is
  invalid.

* Derive Copy and Clone for Light, Projection and Camera types
* Derive Clone for Renderable type