New macro system and stdlib additions

orchid-extension/src/system_ctor.rs

@@ -62,6 +62,8 @@ pub trait SystemCtor: Send + Sync + 'static {
 	type Instance: System;
 	const NAME: &'static str;
 	const VERSION: f64;
+	/// Create a system instance. When this function is called, a context object
+	/// isn't yet available
 	fn inst(deps: <Self::Deps as DepDef>::Sat) -> Self::Instance;
 }