Deduplicate registrar contract & calling logic (#11110)

* Rename RegistryInfo -> RegistryInfoDeprecated

* Add BlockId parameter to Registrar::get_address and RegistrarClient::call_contract

* Remove RegistrarClient::Call (use async for now); add RegistrarClient::get_address

* Remove Registrar type in favour of naked trait

* Use CallContract trait bound instead of separate call_contract method

* Make RegistrarClient::get_address and URLHint::resolve synchronous

* RegistrarClient::get_address: return check if address is zero

* Modify RegistryInfo::registry_address to take &str

* return Result from RegistryInfo::registry_address

* Replace RegistryInfo with RegistrarClient

- Modifed RegistrarClient::registrar_address to return Option
- Removed BlockChainClient::registrar_address

* Fix other build configs

* Fix unit test builds

* Remove local RegistrarClient type from run::execute_impl

* Remove registrar.json from ethcore

* Formatting/line breaks

* Update RegistrarClient docs, remove explicit lifetime

* Weak ref to ethcore client from hash fetch client

* Fix unit tests

ethcore/src/tests/client.rs

@@ -48,6 +48,7 @@ use test_helpers::{
 	generate_dummy_client_with_data, get_good_dummy_block, get_bad_state_dummy_block
 };
 use rustc_hex::ToHex;
+use registrar::RegistrarClient;
 
 #[test]
 fn imports_from_empty() {