Revert and redo #952 (#1133)

* Revert "Pruning changes trie without digests (#952)"

This reverts commit 6f9a505fba.

* pruning changes tries without digests

* u64::max_value()

* Update wasm files and fix merge conflict

* Fixes tests

substrate/srml/system/src/lib.rs

@@ -201,7 +201,6 @@ decl_storage! {
 	}
 	add_extra_genesis {
 		config(changes_trie_config): Option<ChangesTrieConfiguration>;
-		config(_phantom): ::std::marker::PhantomData<T>;
 
 		build(|storage: &mut primitives::StorageMap, _: &mut primitives::ChildrenStorageMap, config: &GenesisConfig<T>| {
 			use codec::Encode;