Prepare Polkadot to be used by Cumulus (#1697)

* Prepare Polkadot to be used by Cumulus

This begins to make Polkadot usable from Cumulus.

* Remove old test

* Reset some changes

* More reverts

* MOARE

* Don't use `unimplemented!`

polkadot/Cargo.lock

@@ -5099,6 +5099,7 @@ dependencies = [
  "sp-core",
  "sp-externalities",
  "sp-io",
+ "sp-runtime",
  "sp-std",
  "sp-wasm-interface",
 ]
@@ -5449,6 +5450,7 @@ dependencies = [
  "sp-offchain",
  "sp-runtime",
  "sp-session",
+ "sp-storage",
  "sp-transaction-pool",
  "sp-trie",
  "substrate-prometheus-endpoint",