Create issues for all TODOs/FIXMEs (#224)

* network and validation

* remainder of todos

* ref new issue

* change issue number

polkadot/validation/src/shared_table/mod.rs

@@ -139,6 +139,7 @@ impl SharedTableInner {
 		let digest = &summary.candidate;
 
 		// TODO: consider a strategy based on the number of candidate votes as well.
+		// https://github.com/paritytech/polkadot/issues/218
 		let do_validation = para_member && match self.validated.entry(digest.clone()) {
 			Entry::Occupied(_) => false,
 			Entry::Vacant(entry) => {