Continue new platform/glium implementations

- Assets, asset manager system
- Rendering system trait
- Kick off glium platform implementation
- And more

raidillon_glium/src/render/basic.rs

@@ -0,0 +1,12 @@
+use glium::Surface;
+use crate::RenderingSystem;
+use crate::system::RenderingContext;
+
+/// A basic renderer pipeline step.
+pub struct BasicRenderingSystem;
+
+impl RenderingSystem for BasicRenderingSystem {
+    fn render<S: Surface>(ctx: &mut RenderingContext<S>) {
+        todo!()
+    }
+}