Make runtime api generate version and identifier information (#1226)

* Make `decl_runtime_apis!` implement `RuntimeApiInfo` for all runtime
apis

* Make the runtime side generate the info constants as well

* Make `RuntimeApiInfo` implementation use the correct generics

* Adds a test for the runtime api info stuff

* Remove duplicated code by using block from `test-client`

* Adds `compile_fail` tests for `api_version`

* Adds documentation for `api_version`

* Make `impl_runtime_apis!` generate `RUNTIME_API_VERSIONS`

* Update documentation and tests for `RUNTIME_API_VERSIONS`

* Implement `has_api` by using the `RuntimeApiInfo`

* Make `impl_runtime_apis` check that trait identifiers are unique

* Prefix all runtime api function with the corresponding trait

So `execute_block` will be called `Core_execute_block`.
This makes it possible to have traits implement a function with the
same name.

* Rebase master

* Update after master rebase

substrate/core/test-runtime/src/lib.rs

@@ -67,12 +67,12 @@ use runtime_version::NativeVersion;
 
 /// Test runtime version.
 pub const VERSION: RuntimeVersion = RuntimeVersion {
-	spec_name: ver_str!("test"),
-	impl_name: ver_str!("parity-test"),
+	spec_name: create_runtime_str!("test"),
+	impl_name: create_runtime_str!("parity-test"),
 	authoring_version: 1,
 	spec_version: 1,
 	impl_version: 1,
-	apis: apis_vec!([]),
+	apis: RUNTIME_API_VERSIONS,
 };
 
 fn version() -> RuntimeVersion {