Make sp_core and sp_runtime dependencies optional, and bump to latest (#760)

* begin porting over traits; remove Config use of Hash

* port over the Header bits that we need

* sp_core_hashing where possible, move Verify to PairSigner, remove unused errors

* tidy up Config things and move related bits into one place

* fix codegen

* copy Era over

* move AccountId, Address, Signer to Signer trait and a pass over fixing examples

* impl MultiAddress, MultiSignature, AccountId32 and add back to Config (for decoding later)

* Copy over StorageKey, StorageData, StorageChangeSet

* subxt core compiling with no sp_core or sp_runtime

* Get examples compiling

* pass over fixing tests

* cargo fmt

* clippy tweaks and update polkadot.rs

* fix codegen docs

* port over special DigestItem encoding/decoding

* clippy and doc fixes

* cargo fmt and example fix

* more cargo fmt-ing...

* substrate-extra to substrate-compat

* cargo.toml comments

* simplify PairSigner trait bounds

* move RPC types to a separate file

* fix docs

* Add some tests for things and other PR feedback

* bump to latest sp deps

* avoid needing substrate-compat feature in a test

subxt/src/storage/storage_client.rs

@@ -16,15 +16,15 @@ use crate::{
         DecodeWithMetadata,
         Metadata,
     },
+    rpc::types::{
+        StorageData,
+        StorageKey,
+    },
     Config,
 };
 use derivative::Derivative;
 use frame_metadata::StorageEntryType;
 use scale_info::form::PortableForm;
-use sp_core::storage::{
-    StorageData,
-    StorageKey,
-};
 use std::{
     future::Future,
     marker::PhantomData,