New Event Subscription API (#442)

* Add reworked event types

* first pass implementing event subscriptions

* make clear that some methods are private

* comment tidy

* use Events in transaction stuff

* align transaction and event APIs

* remove __private_ prefixes; they are ugly

* fix examples and remove old events and subscription code

* better comments on hidden event functions

* re-add find_first_event; it's used a bunch in tests and examples

* cargo check --all-targets now passes

* Fix up existing event tests

* cargo fmt

* change todo to note

* clippy and doc niggles

* revert to find_first_event

* Add specific subscription related tests

* cargo fmt

* Update tests and add/fix examples

* cargo fmt

* add a little to subscribe_all_events example

* cargo fmt

* move an example comment

* easy access to root mod for more clarity

* add a couple of tests to ensure that events properly decoded until naff bytes

* Simplify EventSubscription Stream impl a little

* Address some PR feedback

subxt/src/lib.rs

@@ -59,12 +59,11 @@ use derivative::Derivative;
 mod client;
 mod config;
 mod error;
-mod events;
+pub mod events;
 pub mod extrinsic;
 mod metadata;
 pub mod rpc;
 pub mod storage;
-mod subscription;
 mod transaction;
 
 pub use crate::{
@@ -86,8 +85,9 @@ pub use crate::{
         TransactionError,
     },
     events::{
-        EventsDecoder,
-        RawEvent,
+        EventDetails,
+        Events,
+        RawEventDetails,
     },
     extrinsic::{
         DefaultExtra,
@@ -114,11 +114,6 @@ pub use crate::{
         StorageEntryKey,
         StorageMapKey,
     },
-    subscription::{
-        EventStorageSubscription,
-        EventSubscription,
-        FinalizedEventStorageSubscription,
-    },
     transaction::{
         TransactionEvents,
         TransactionInBlock,