Make Polkadot use the Substrate traity libraries (#105)

* Initial stuff.

* Various fixes.

* Fix tests.

* Fix another test

* Fix another test.

* Docs in polkadot runtime.

* Fix up ser/de tests.

* Update god keys

* Syntax

* Fix

* Merge remote-tracking branch 'origin/master' into gav-merge-runtime

* Permissions on init.sh

* Port-over the whitespace from @rphmeier

* Rename

* Merge branch 'master' into gav-merge-runtime

* Fix typo.

* Fix grumbles.

* Make more idiomatic.

* Move `Ed25519Signature` out of traits.