Fix several RPCs (#1926)

* Fix up pending receipts details.

* Add support for additional params and registry over RPC.

* Fix tests.

* Add test, additional fix.

Fixes #1932.

* Fix up tests.

* Fix test.

* Fix test.

ethcore/res/ethereum/morden.json

@@ -8,7 +8,7 @@
 				"difficultyBoundDivisor": "0x0800",
 				"durationLimit": "0x0d",
 				"blockReward": "0x4563918244F40000",
-				"registrar": "",
+				"registrar": "0x8e4e9b13d4b45cb0befc93c3061b1408f67316b2",
 				"frontierCompatibilityModeLimit": "0x789b0"
 			}
 		}