Convert all UK spelling to US (#2138)

* all the ise

* forgot a misspelling

* a few more replacements

* bump impl

* rollback and fixes

* bump impl again

* Add aliases for RPC

* Update on_demand.rs

substrate/core/sr-api-macros/tests/decl_and_impl.rs

@@ -74,7 +74,7 @@ impl_runtime_apis! {
 		fn execute_block(_: Block) {
 			unimplemented!()
 		}
-		fn initialise_block(_: &<Block as BlockT>::Header) {
+		fn initialize_block(_: &<Block as BlockT>::Header) {
 			unimplemented!()
 		}
 	}