Ensure timestamp config makes sense. (#2132)

* Timestamp period should be expressed as expected period

* Fix test

* Ensure value never illegal

* Rename

* Remove println

* Add default

* Comment

* Fix, bump and rebuild wasm

* Fix test

* Add TODOs

* Configure only minimum_period.

* Fix

* Update srml/timestamp/src/lib.rs

Co-Authored-By: gavofyork <github@gavwood.com>

* Update srml/timestamp/src/lib.rs

Co-Authored-By: gavofyork <github@gavwood.com>

substrate/srml/aura/src/lib.rs

@@ -165,7 +165,7 @@ impl<T: Trait> Module<T> {
 	pub fn slot_duration() -> u64 {
 		// we double the minimum block-period so each author can always propose within
 		// the majority of their slot.
-		<timestamp::Module<T>>::block_period().as_().saturating_mul(2)
+		<timestamp::Module<T>>::minimum_period().as_().saturating_mul(2)
 	}
 
 	fn on_timestamp_set<H: HandleReport>(now: T::Moment, slot_duration: T::Moment) {

substrate/srml/aura/src/mock.rs

@@ -68,7 +68,7 @@ pub fn new_test_ext(authorities: Vec<u64>) -> runtime_io::TestExternalities<Blak
 		authorities: authorities.into_iter().map(|a| UintAuthorityId(a)).collect(),
 	}.build_storage().unwrap().0);
 	t.extend(timestamp::GenesisConfig::<Test>{
-		period: 1,
+		minimum_period: 1,
 	}.build_storage().unwrap().0);
 	t.into()
 }