Proper default accounts RPCs (#4580)

* Default accounts setting - account provider

* RPC support for default accounts

* Updating JS code

* Rename whitelist to addresses

rpc/src/v1/impls/light/eth.rs

@@ -187,7 +187,7 @@ impl Eth for EthClient {
 
 		let accounts = self.accounts
 			.note_dapp_used(dapp.clone())
-			.and_then(|_| self.accounts.dapps_addresses(dapp))
+			.and_then(|_| self.accounts.dapp_addresses(dapp))
 			.map_err(|e| errors::internal("Could not fetch accounts.", e))
 			.map(|accs| accs.into_iter().map(Into::<RpcH160>::into).collect());