Use the generated DispatchError instead of the hardcoded Substrate one (#394)

* WIP DispatchError generic param

* main crate now compiling with new E generic param for DispatchError

* Remove E param from RpcClient since it doesn't really need it

* Point to generated DispatchError in codegen so no need for additional param there

* More error hunting; cargo check --all-targets passes now

* Use our own RuntimeVersion struct (for now) to avoid error decoding into sp_version::RuntimeVersion

* cargo fmt

* fix docs and expose private documented thing that I think should be pub

* move error info to compile time so that we can make DispatchError a little nicer to work with

* cargo fmt

* clippy

* Rework error handling to remove <E> param in most cases

* fix Error doc ambiguity (hopefully)

* doc tweaks

* docs: remove dismbiguation thing that isn't needed now

* One more Error<E> that can be a BasicError

* rewrite pallet errors thing into normal loops to tidy

* tidy errors codegen a little

* tidy examples/custom_type_derives.rs a little

* cargo fmt

* silcnce clippy in example

examples/custom_type_derives.rs

@@ -14,9 +14,13 @@
 // You should have received a copy of the GNU General Public License
 // along with subxt.  If not, see <http://www.gnu.org/licenses/>.
 
+#![allow(clippy::redundant_clone)]
+
 #[subxt::subxt(
     runtime_metadata_path = "examples/polkadot_metadata.scale",
-    generated_type_derives = "Clone, Debug"
+    // We can add (certain) custom derives to the generated types by providing
+    // a comma separated list to the below attribute. Most useful for adding `Clone`:
+    generated_type_derives = "Clone, Hash"
 )]
 pub mod polkadot {}
 
@@ -25,6 +29,6 @@ use polkadot::runtime_types::frame_support::PalletId;
 #[async_std::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let pallet_id = PalletId([1u8; 8]);
-    let _ = <PalletId as Clone>::clone(&pallet_id);
+    let _ = pallet_id.clone();
     Ok(())
 }