Expose instancing in metadata (#3188)

* Expose instancing in metadata

- Introduces metadata v7
- If a module is using instancing, the storage exposes the instance in
metadata
- Metadata module name is now the upper case one given to
`construct_runtime!`

* Remove obsolete macro

* Just expose one prefix

* Bump spec

* Fix prefix generation

substrate/srml/support/src/runtime.rs

@@ -576,7 +576,9 @@ macro_rules! __decl_runtime_metadata {
 			$runtime;
 			{
 				$( $parsed )*
-				$module $( < $module_instance > )?  { $( $( $leading_module )* )? $( $modules )* }
+				$module $( < $module_instance > )? as $name {
+					$( $( $leading_module )* )? $( $modules )*
+				}
 			};
 			$( $rest )*
 		);
@@ -618,11 +620,18 @@ macro_rules! __decl_runtime_metadata {
 	// end of decl
 	(
 		$runtime:ident;
-		{ $( $parsed_modules:ident $( < $module_instance:ident > )? { $( $withs:ident )* } )* };
+		{
+			$(
+				$parsed_modules:ident $( < $module_instance:ident > )? as $parsed_name:ident {
+					$( $withs:ident )*
+				}
+			)*
+		};
 	) => {
 		$crate::impl_runtime_metadata!(
 			for $runtime with modules
-				$( $parsed_modules::Module $( < $module_instance > )? with $( $withs )* , )*
+				$( $parsed_modules::Module $( < $module_instance > )? as $parsed_name
+					with $( $withs )* , )*
 		);
 	}
 }