Blocks carry full attestations for candidates (#42)

* statement table yields fully-attested candidates

* attestation types in polkadot-primitives

* propose block with fully-attested candidates in consensus

* some signature-checking logic in the runtime

* fix runtime compilation

* ensure attestations are full and without duplicate when checking

* fix consensus-service compilation

* add some tests

* use bitvec from crates.io now that it's published

* sign statements based on primitive statement's encoding

* remove some serialize bounds

* Fix error message with duplicate availability attestations

Co-Authored-By: rphmeier <rphmeier@gmail.com>

polkadot/runtime/src/lib.rs

@@ -20,6 +20,9 @@
 // `construct_runtime!` does a lot of recursion and requires us to increase the limit to 256.
 #![recursion_limit="256"]
 
+#[macro_use]
+extern crate bitvec;
+
 #[macro_use]
 extern crate parity_codec_derive;
 extern crate parity_codec as codec;
@@ -52,6 +55,9 @@ extern crate srml_treasury as treasury;
 
 extern crate polkadot_primitives as primitives;
 
+#[cfg(test)]
+extern crate substrate_keyring as keyring;
+
 mod parachains;
 
 #[cfg(feature = "std")]