Skeleton of the Router module (#1726)

The purpose of this commit is to establish a foundation of the router module, it paves the way for the implementation of other features.

polkadot/runtime/parachains/src/lib.rs

@@ -20,7 +20,6 @@
 //! particular the `Initializer` module, as it is responsible for initializing the state
 //! of the other modules.
 
-
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use sp_std::result;
@@ -33,6 +32,7 @@ pub mod inclusion;
 pub mod inclusion_inherent;
 pub mod initializer;
 pub mod paras;
+pub mod router;
 pub mod scheduler;
 pub mod validity;