Update Substrate to rc4 (#175)

* Bump Substrate to rc4

* Add BaseCallFilter type

* Add DenyUnsafe to SystemApi extension

* Use new ServiceBuilder build functions

* Add BaseCallFilter to test runtimes

* Remove old comments

* Add `rev` and `git` fields back

Turns out that if you don't have these future release candidates will
be used if available. For instance, once `rc5` is released a fresh pull
would use that instead of `rc4` which is what we want.

* Use tag release instead of specific commit

Will make scripted updates easier in the future

* Add short script to update between `rc` versions

* Update scripts/update_rc.sh

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

bridges/bin/node/runtime/src/lib.rs

@@ -157,6 +157,8 @@ parameter_types! {
 }
 
 impl frame_system::Trait for Runtime {
+	/// The basic call filter to use in dispatchable.
+	type BaseCallFilter = ();
 	/// The identifier used to distinguish between accounts.
 	type AccountId = AccountId;
 	/// The aggregated dispatch type that is available for extrinsics.