Allow modules to validate transaction, second attempt (#2463)

* first impl

* rename origin::inherent to none

* fix

* fix

* Apply suggestions from code review

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* comment

* better error

* doc

* (add unsigned module 🤦)

* doc

* fix

* implement for node-template as well

* add validated unsigned to executor

* fix

* fix

* bump version

* testing xt

* remove extraneous logic

* licence

* impl test

substrate/srml/contract/src/lib.rs

@@ -476,7 +476,7 @@ decl_module! {
 				Some(system::RawOrigin::Signed(ref account)) if aux_sender.is_none() => {
 					(true, account)
 				},
-				Some(system::RawOrigin::Inherent) if aux_sender.is_some() => {
+				Some(system::RawOrigin::None) if aux_sender.is_some() => {
 					(false, aux_sender.as_ref().expect("checked above"))
 				},
 				_ => return Err("Invalid surcharge claim: origin must be signed or \