Add Assets module (#925)

* Add Assets module

* Fixes

* Fix

* Update comments

* Support `GenesisConfig` without any fields

Fixes: #923

* Do not generate an empty `GenesisConfig`, instead generate no `GenesisConfig`

substrate/core/sr-primitives/src/lib.rs

@@ -269,19 +269,32 @@ pub fn verify_encoded_lazy<V: Verify, T: codec::Encode>(sig: &V, item: &T, signe
 
 #[macro_export]
 macro_rules! __impl_outer_config_types {
-	($concrete:ident $config:ident $snake:ident $($rest:ident)*) => {
+	(
+		$concrete:ident $config:ident $snake:ident < $ignore:ident > $( $rest:tt )*
+	) => {
 		#[cfg(any(feature = "std", test))]
 		pub type $config = $snake::GenesisConfig<$concrete>;
 		__impl_outer_config_types! {$concrete $($rest)*}
 	};
+	(
+		$concrete:ident $config:ident $snake:ident $( $rest:tt )*
+	) => {
+		#[cfg(any(feature = "std", test))]
+		pub type $config = $snake::GenesisConfig;
+		__impl_outer_config_types! {$concrete $($rest)*}
+	};
 	($concrete:ident) => ()
 }
 
 #[macro_export]
 /// Implement the output "meta" module configuration struct.
 macro_rules! impl_outer_config {
-	( pub struct $main:ident for $concrete:ident { $( $config:ident => $snake:ident, )* } ) => {
-		__impl_outer_config_types! { $concrete $( $config $snake )* }
+	(
+		pub struct $main:ident for $concrete:ident {
+			$( $config:ident => $snake:ident $( < $generic:ident > )*, )*
+		}
+	) => {
+		__impl_outer_config_types! { $concrete $( $config $snake $( < $generic > )* )* }
 		#[cfg(any(feature = "std", test))]
 		#[derive(Serialize, Deserialize)]
 		#[serde(rename_all = "camelCase")]

substrate/core/sr-primitives/src/traits.rs

@@ -566,5 +566,5 @@ pub trait ProvideInherent {
 pub trait Extrinsic {
 	/// Is this `Extrinsic` signed?
 	/// If no information are available about signed/unsigned, `None` should be returned.
-	fn is_signed(&self) -> Option<bool>;
+	fn is_signed(&self) -> Option<bool> { None }
 }